Hi Pratigyav,
The scoring algorithm on the Official GMAT is far more complicated than most people realize. Since that algorithm is proprietary, no GMAT company has an exact match for it, thus practice CAT scores can vary based on the 'biases' involved in their respective designs.
The 'accuracy' of a CAT score is also based on how realistically YOU choose to take 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. The most realistic CATs available are the 6 from GMAC (the 2 free CATs, and each of the 2 that come with Exam Pack 1 and Exam Pack 2), so it would be useful to know how you performed on one of those CATS. Once you have that score result, you should post back here and we can talk through what all of this data means.
1) What is your goal score?
2) When are you planning to take the GMAT?
GMAT assassins aren't born, they're made,
Rich