For nearly a decade I was a Labor MP in the NSW parliament. One of the very first things I learned was that we were never, ever, ever permitted to leave the parliament without the whip’s approval. It didn’t matter if you were attending your mother’s funeral or popping out for dinner, if the whip hadn’t signed you out, you weren’t going anywhere.

For a year or so after retiring from politics, I would still get the urge to call the whip’s office and ask if it was OK to duck out for a coffee or a sandwich.

For the life of me, I can’t understand how the Turnbull government, with just a one-seat majority, seemed to have no process in place to ensure that it could always win a vote on the floor of the parliament. And boo-hoo to those Coalition MPs who are calling Labor’s parliamentary tactics, like moving a motion just before parliament finishes, a “stunt”. If parliament is sitting, it is sitting. Stay there and do your damn jobs.

By the way, don’t you love the irony that the people who want to cut penalty rates, which primarily benefit low-income workers, also think it’s just fine to nick off out of their $200,000-a-year jobs early on a Thursday afternoon?

You bet they do. You bet I am.

Speaking of Tony Abbott, sources close to the former PM told my Sky News colleague Peter van Onselen – via a text message sent while we were live on air, no less – that, as prime minister, if he had to be away from parliament, Mr Abbott always had a pair. (And by that, I mean a registered and excused absence, reciprocated by the opposition).

Mr Abbott didn’t miss a vote on Thursday afternoon either. Malcolm Turnbull did miss a vote. Turnbull missed the 4.15 division, which the government won by one vote. Subsequent inquiries confirmed two things: one, that Turnbull was giving a speech at the time, and two, that Turnbull didn’t have a pair.

Makes you think.

You know what else Abbott and his treasurer Joe Hockey could do that their successors Turnbull and Morrison can’t? Maths.

Yep, say what you will about the 2014 budget of horrors, but one thing you can’t say is that it didn’t add up. The measures were woeful and unfair and now destined to exist as zombies, not allowed to live, but not able to be killed off by their creators.

But the maths was correct.

Not so for Messrs Turnbull and Morrison. What a pair these two are. Their omnibus savings bill – their big idea, their big stab at budget savings, their big stick to whack at the opposition – didn’t add up. It was off by $107m! And this wasn’t some buried detail on page 362. This was in a summary table on page five. Page five!

Let’s consider how many eyes in the Turnbull government supposedly reviewed this bill: treasurer Morrison and his staff; the prime minister and his staff; the cabinet, who would have approved it; the Coalition party room, who would have approved it.

Apparently none of these people own calculators. Or read beyond page four.

It took the opposition’s economic team, led by Jim Chalmers and Chris Bowen, less than a day to find the $107m error. In fact, the opposition noticed it the night before in a draft of the legislation they were provided by the government, and just assumed it was a typo that would be fixed in the final legislation.

It was that unfathomable to the opposition that the government, with all those eyes looking at its legislation, had actually made a “computational error”. But that’s exactly what Morrison called it the next day after he was forced to admit the mistake – a computational error. This may make Scott Morrison the first treasurer in Australian history to openly acknowledge that maths is not his strong suit.

One person who can add up fairly accurately is Labor senator Sam Dastyari. We already know his facility with numbers, given the success of Labor leadership challenges mark I (Gillard) and mark II (Rudd). Senator Dasher is devastatingly accurate when it comes to paying his bills, securing a Chinese-Australian company to pay his very specific electorate overspend allowance of $1670.82 (which he did declare).

Imagine if we could channel that kind of diligent precision to the budget deficit.

Why did the senator get a Chinese-linked company to pay his bills? I’d rather try to explain something simpler, like how there are three persons in one in the Holy Trinity, or how it is that Saint Mother Teresa cured a woman of her cancer.

Really, I would rather that Senator Dastyari explain this, in more detail, than he has to date. And really, really, I would prefer that Australian parliamentarians decided to ban foreign political donations altogether.

Maybe one day they will.

But for next sitting week, let’s set some realistic goals for our federal MPs. Let’s try to stay at work until parliament finishes, and get our numbers to add up correctly. And don’t forget that all members, including prime ministers, still need a pair.