Hi Nick90,
The scoring algorithm on the Official GMAT is far more complicated than most people realize. It takes into account a number of different factors - far more than just the number of correct answers. As such, you shouldn't be spending time trying to figure it all out. You'd be better served working on building up your skills. A far more useful gauge would be to review each CAT and determine how many questions you SHOULD have gotten correct, but didn't (due to a silly/little mistake). Those mistakes are the things that you have to fix to score at a higher level.
From your profile, you already appear to have scored 750 on the Official GMAT (which is an outstanding score that 98% of Test Takers will never achieve in their lives), so why are you still studying?
GMAT assassins aren't born, they're made,
Rich