Just to lay out a few details based on this article explaining that Obama continues to waver on what parts of the 2005 Bradbury torture memos to reveal. (h/t Steve)
I've put this detail in a series of posts, but it really deserves a full post. According to the May 30, 2005 Bradbury memo, Khalid Sheikh Mohammed was waterboarded 183 times in March 2003 and Abu Zubaydah was waterboarded 83 times in August 2002.
On page 37 of the OLC memo, in a passage discussing the differences between SERE techniques and the torture used with detainees, the memo explains:
The CIA used the waterboard "at least 83 times during August 2002" in the interrogation of Zubaydah. IG Report at 90, and 183 times during March 2003 in the interrogation of KSM, see id. at 91.
Note, the information comes from the CIA IG report which, in the case of Abu Zubaydah, is based on having viewed the torture tapes as well as other materials. So this is presumably a number that was once backed up by video evidence.
The same OLC memo passage explains how the CIA might manage to waterboard these men so many times in one month each (though even with these chilling numbers, the CIA's math doesn't add up).
...where authorized, it may be used for two "sessions" per day of up to two hours. During a session, water may be applied up to six times for ten seconds or longer (but never more than 40 seconds). In a 24-hour period, a detainee may be subjected to up to twelve minutes of water appliaction. See id. at 42. Additionally, the waterboard may be used on as many as five days during a 30-day approval period.