During the exam, they ask you a variety of questions about your experience. Then, you answer 160 questions, which is probably the entire question pool. You provide feedback.
Sun will probably look at the results and see which questions are too easy, and which are too hard, and which just don't make sense or got bad feedback. They'll then create the 'real' exam pool from their results, and then figure out what a reasonable pass score would be. I'm guessing that it is after that when they will send out test takers their real scores.
That's all conjecture of course, but it is what has happened in the past. Past test score passes aren't always a good indicator of future required scores. I've seen some major swings in the required scores for SCJP versions over the years.