Typically, the absentees that arrived prior to today are counted first.
That's why the typical CA election results start great (wow, Bush is ahead in CA!?!?!?!?) and then drift away.
Then we are hosed. I bet the absentee voters that wait until the last day to mail it in are 50-50 at best, since it takes a procrastinator to sit on the ballot until the last day. I was hoping that the ones that mailed it in days ago have not yet been counted since those are probably much more favorable to us.