hadley: That's a great question, which I've talked about on some of my earlier yearly reports. Basically, not every screener leak is an Academy screener... It may be a screener sent months before Oscar time to critics, distributors, or judges for other awards.
The "Screener Release" column is the date that an Academy member received his screeners, and the "Screener Leak" is the date that any screener first leaked to the Internet.
The piracy scene almost never states where the screeners come from, so it's impossible for me to tell whether the leaked screener was an official Academy screener or not. On my Statistics sheet, I try to make a best guess by only counting screeners that leaked online after the official Academy screener date. (There was an error in my "# Academy screeners leaked (probable)" column, which is now fixed.)
Only 93 out of 165 screeners were leaked after the Academy screener release date, so there should be a total of 72 screeners that were leaked on or before the date Academy screeners were received.