Hi lorenzoboole,
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 CAT scores can vary a bit based on the 'biases' involved in their respective designs. The most realistic CATs available are the 6 from GMAC, but the CATs from Kaplan,
MGMAT and Veritas are all 'close enough' to the real thing that they will provide you with a relatively realistic score assessment (assuming that you properly take the CAT in a realistic fashion the matches up with how you will take your Official GMAT).
Both 690 and 730 are outstanding initial CAT Scores (the average score on the Official GMAT hovers around 550 most years). By extension, you are likely a really strong overall critical thinker. Going forward, to receive the most accurate CAT/mock results, you have to be strict about making sure you mirror as many aspects of Test Day as you reasonably can when you take your CATs.
Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
1) Besides the book that you mentioned, what study materials do you currently have access to?
2) What is your overall goal score?
3) When are you planning to take the GMAT?
4) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich