Hi gmathopeful90,
The scoring algorithm on the Official GMAT is far more complicated than most people realize. It takes into account a number of different factors, including the relative difficulty of the question, whether you were expected to get it correct or not, the placement of the question, what's going on "around it", the "strings" of correct and incorrect answers, whether the question even counts or not (some questions are "experimental" and are worth 0), if you leave questions unanswered and incur a penalty, etc.
While there are many brand-name CATs that can provide a reasonable score assessment of your abilities, none of them has the exact same algorithm as the Official GMAT. A far more useful gauge (other than the number of correct/incorrect answers) would be to review the 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.
Have you taken any of the GMAT Prep CATs yet? If so, then how did you score?
GMAT assassins aren't born, they're made,
Rich