The government says you can't know how many people U.S. drone strikes have killed, because that's a state secret. But one of the most hawkish members of the U.S. Senate just said the strikes have killed 4,700 people. And his math raises questions.

That's what Sen. Lindsey Graham (R-South Carolina) approvingly told an Easley, South Carolina, Rotary Club on Tuesday afternoon. It's the first public death toll provided by a U.S. government official for the signature method of killing in the U.S.' sprawling, global counterterrorism campaign.

"We've killed 4,700," Graham said, according to an Easley website. "Sometimes you hit innocent people, and I hate that, but we're at war, and we've taken out some very senior members of al-Qaida." Graham did not evidently offer an estimate of how many innocent people the drones have killed.

Graham staffers did not return voicemails and e-mails seeking elaboration. (We'll update if they do.) But that's a very high figure – at least as it pertains to the CIA's drone strikes, outside the declared battlefields of Iraq and Afghanistan, which is what the context of Graham's remarks make it seem like he's referring to. As Micah Zenko of the Council on Foreign Relations blogs, that's on the highest end of the drone-death estimate compiled by the Bureau of Investigative Journalism from publicly available news reports. Zenko's compilation of the averages of non-governmental organizations' guesstimates for drone casualties is about 1,700 people lower.

The CIA declined to comment about whether Graham revealed classified information. Counting the death toll from drones is a notoriously imprecise, murky business.

Graham's death count would raise questions about the much-vaunted precision of the strikes. Using the Bureau of Investigative Journalism's count, the U.S. has launched between 416 and 439 drone strikes in Yemen, Pakistan and Somalia since the U.S. first successfully weaponized an MQ-1 Predator a decade ago. If Graham's right, each strike would have to kill more than 10 people. It's certainly possible – the 100-pound Hellfire missile carried by the drones is capable of it – but U.S. counterterrorism officials typically describe the drones as a tool geared for the targeting of a specific terrorist at a time, with minimal civilian casualties. (That isn't necessarily the case: Sometimes the CIA kills people with drones without knowing who exactly they are.)

Yet Graham's count is simultaneously low. Judging from the context of his remarks, he's evidently not counting the U.S. military's drone strikes in Iraq and Afghanistan. So the real number of deaths from the strikes between the covert CIA drone program and the U.S. military's still rarely acknowledged efforts is likely even higher.

It wouldn't be the first time that a U.S. senator has offhandedly revealed specific and unacknowledged information about the drones. In 2009, Sen. Dianne Feinstein (D-California), the chairwoman of the Senate intelligence committee, blabbed that the Pakistani government was hosting CIA drones for strikes on Pakistanis.

But Graham's disclosure underscores the extraordinary secrecy around the centerpiece of U.S. counterterrorism efforts – a military action in all but name, operated by an agency that need not explain to the public how it carries out the program. Even Feinstein, a big advocate of the CIA and its drones, acknowledged to Danger Room earlier this month that the CIA has a history of being deceitful with Congress about its other highly valued programs. And even after the CIA's likely next director, John Brennan, acknowledged that the CIA performs such lethal strikes, the Justice Department still maintains that even the existence of its drone program is a state secret, so that it need not disclosure information about it in court. Whatever Graham's intentions in stating a death toll – regardless of its accuracy – that secrecy is the most prominent, visible fact about the drones.