Hi btan219,
These two practice scores are not as far apart as they might appear. GMAC has publicly stated that the Official Score that you earn on Test Day is within +-30 points of actual ability. Assuming a similar 'swing' in how practice CATs function, these two scores point to a general ability in the low 500s.
As far as "data" is concerned, the percentiles and number of correct answers are both dubious pieces of information. A percentile is just a measure of "where you are in line" compared with the other people who took that Test. The scoring algorithm on the Official GMAT is far more complex than most people realize and the calculation involves a number of different factors, including which questions you got correct and incorrect, the relative difficulty of the question, whether you were expected to get it correct or not, whether it even counted or not (some questions are 'experimental' and are worth 0), the 'strings' of answers, if you ran out of time and left questions unanswered, etc.
The 'accuracy' of a CAT score is also based on how realistic YOU choose to make the CAT. If you skip sections, pause the Test, take it at home, take it at a different time of day as your Official GMAT, do anything else that is unrealistic, etc., then your score is likely to be less accurate.
1) What is your goal score?
2) When are you planning to take the GMAT?
GMAT assassins aren't born, they're made,
Rich