If you take President-elect Donald Trump at his word, according to what he told 60 Minutes’ Lesley Stahl in his first interview since the election, the overwhelming majority of unauthorized immigrants in the US have nothing to fear from his administration.

“What we are going to do is get the people that are criminal and have criminal records, gang members, drug dealers,” he told Stahl. Most unauthorized immigrants don’t have criminal records. If the Trump administration actually limited its deportation efforts to convicted criminals, it would be more lenient than the Obama administration has ever been.

The problem is that the president-elect doesn’t understand that. He told Stahl that there are “probably 2 million, it could even be 3 million” unauthorized immigrants with criminal records in the US — and that he wanted to deport all of them.

The Trump administration isn’t going to be able to deport 2 or 3 million “criminal illegal immigrants,” because there simply aren’t that many people who fit the description. If it wants to deport 2 to 3 million people, it’s going to have to scoop up a lot of people who don’t already have criminal convictions.

Deporting 2 to 3 million immigrants in a single term as president would be something we’ve never seen in America. It would put every unauthorized immigrant in the US under a one in four chance of being separated from family, thrown in jail, or sent back to a country that many of them haven’t set foot in for years.

Take President-elect Trump at his word, and unauthorized immigrants have nothing to fear from him. Look at the implications of his promises, though, and they have everything to fear.

There probably aren’t 2 or 3 million unauthorized immigrants with criminal records in the US — and there never has been

The reason there’s so much uncertainty about Trump’s plan is that it’s based on a false premise. And when you’re making policy based on a false premise, you end up facing a choice: Stick to the game plan — even if it doesn’t get the results you want — or do whatever is needed to make it look like you were right all along.

Unsurprisingly, the core of Trump’s argument is a bogus statistic. He’s promising to deport “people who are criminal and have criminal records” who are also “here illegally” — and then saying there are “probably 2 million, it could even be 3 million” of such people.

The stretch to 3 million is sheer Trumpian exaggeration. But the 2 million is rooted in an official government estimate — of something else.

In its budget request for the 2013 fiscal year (written in early 2012), the Department of Homeland Security requested extra money to identify and deport immigrants living in the United States who’d been convicted of crimes. It explained the need for the cost by pointing out that the government had never been able to track all “removable criminal aliens”:

ICE estimates that approximately 900,000 arrests of aliens for crimes occur every year and that approximately 550,000 criminal aliens convicted of crimes exit law enforcement custody every year. ICE has never had the capability to identify, arrest and remove all of these criminal aliens. ICE estimates that 1.94 million removable criminal aliens are in the United States today.

This estimate was basically an educated guess — and it was based on data that was already a few years old when ICE wrote the report.

ICE looked at the number of immigrants in the United States according to the 2008 American Community Survey, looked at a Department of Justice report (with data that ended in 2001) about the number of Americans who’d been in prison, and extrapolated accordingly.

It’s not clear whether there were ever 1.9 million “removable criminal aliens.” It’s certainly likely that after eight years of an Obama administration that’s implemented immigration checks in prisons and jails all over the country and deported hundreds of thousands of “criminal aliens,” there are fewer than 1.9 million left. After all, ICE made that estimate to request more money from Congress to deport these people — and the money was granted.

And, crucially, it’s not clear how many “removable criminal aliens” are also unauthorized immigrants. Despite what President-elect Trump says, the two are not the same: An immigrant can be “removable” because he’s unauthorized, but he can also become removable once convicted of a crime that strips him of his legal status.

The Trump administration’s first 100 days’ plan promises to start removing “the more than 2 million criminal illegal immigrants from the country.” But the population of “criminal illegal immigrants” is a subgroup of the “removable criminal aliens” that ICE once estimated to number 2 million. And who knows how many of those are left.

The Trump administration is getting rid of the policies that focused deportation efforts on criminals

Obviously, it matters intrinsically that the president-elect of the United States is building one of his chief administration policy priorities on a statistic that’s essentially a lie. Even if there were 2 million unauthorized immigrants with criminal records in the US, the US government doesn’t know where all of them are. The number of immigrants with criminal records who’ve recently been released from custody amounts to fewer than 200,000.

Since the Trump administration won’t be able to do what it promises, though, the question becomes what it will do instead. And here’s where things get sticky.

If the Trump administration really stuck to deporting or detaining “criminal illegal immigrants” — if it didn’t deport any unauthorized immigrant who hadn’t been convicted of a crime — it would be more lenient than the Obama administration has ever been toward the unauthorized.

Right now (thanks to a policy that’s been in place since late 2014), ICE agents are instructed to focus on people convicted of crimes, people who’ve entered the US since 2013, and people who already have deportation orders. Taking the Trump administration at its word about “criminal illegal immigrants,” it would only target the first of those.

But the only way to focus resources on a particular group of unauthorized immigrants is to tell immigration agents not to spend their resources on other groups of unauthorized immigrants — to tell agents whom they should and shouldn’t deport.

In other words, it requires doing exactly what President-elect Trump has promised not to do: directing immigration agents only to “enforce the law” in particular cases.

Many agents think their job is to apprehend and deport anyone who’s violated immigration law — the idea of focusing on people who’ve also broken criminal laws just doesn’t make any sense to them. They’ve been in semi-open rebellion against the Obama administration, and they rallied around a candidate, Donald Trump, who promised to let them do their jobs.

President-elect Trump has promised to dismantle the programs that allowed the Obama administration to protect particularly “terrific” immigrants from deportation — like the 2012 Deferred Action for Childhood Arrivals program.

Without another way to tell agents what to do (in a way that forces them to comply), the Trump administration wouldn’t be any more effective than the Obama administration was during its first term, when it told agents to focus on “criminals” but wasn’t able to do anything when agents decided to go after people who were simply here without papers.

Deport 2 million people first, label them “criminals” later?

Even when there was evidence that immigration agents weren’t just going after convicted criminals, though, President Obama and his White House claimed they were. And the official statistics collected by ICE certainly indicated that at least half of their record numbers of deportees were “criminal aliens.”

Plenty of “criminal aliens,” though, weren’t threats to public safety. Many were just people who’d come into immigration custody through the criminal justice system after being picked up by local police or booked into a local jail. In practice, this created an incentive to engage in racial profiling: Pull over someone who “looks illegal” for a traffic violation, book him for driving without a license, turn him over to immigration agents, tally him up as a “criminal alien.”

The Trump administration has promised to restore the programs that gave local police most power to help enforce immigration law. It’s going to have a lot of unauthorized immigrants come into contact with the criminal justice system — most of whom wouldn’t be considered “removable criminal aliens” if you looked at their records today.

It would be very easy for the Trump administration to deport as many people as possible and simply claim it’s doing it because they’re criminals. Immigration agents won’t disagree: Many of them see all unauthorized immigrants as criminals. The public may not know any better. After all, President Trump will say they’re going after criminals.

The only people who will know the truth will be immigrants themselves, who will live under the constant fear of detention and deportation — and for whom the fact that they aren’t convicted criminals will, they know, be no protection.

Watch: The racist history of US immigration policy