They take you upstairs and talk about the company a little, then they get right to the ATP type written exam.
I think they give like an hour or two for the test, can't remember exactly.
Then after everybody finishes you go downstairs and you either go to the 2 on 1 interview or you go to the computer test which envolves number matching, colors, memorization skills, etc. etc.
If it turns your brain into soft noodles the test did its thing, they are just looking to see how you do under pressure AND how good you score, its also timed. I have heard they put alot of emphisis on the score though, whether they still do or not I don't know.
Just a hint, do not say how hard it is while doing the test or anything negative about, they are also looking for good attitudes.
After that, you are pretty much done. Lots of nice folks there and it is a pleasant aptmosphere, it is very laid back.