Hi hani1024,
To be clear, if your Score Goal is 600 or higher, then you likely have the skills RIGHT NOW to hit that Goal. However, if you actually want to score a lot higher than 600, then we need to properly define what that Score is (since you'll have to develop new skills to earn a much higher Score).
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 your CATs function, your 2 CAT score results - along with your Official Score - show that you essentially performed the same each time (about 560+/- a few points). You handle certain aspects of the GMAT consistently well, but you also make certain consistent mistakes.
Your last practice CAT Score is fairly close to your Official Score, so we can use that CAT as a reference. "Review" is an exceptionally important part of the GMAT training process; your ability to define WHY you're getting questions wrong is essential to defining the areas that you need to work on (and the specific things that you need to 'fix'). As such, I'd like to know a bit more about your last CAT. While a full Mistake Tracker would provide a lot more information, there are some basic questions that you should be able to answer (and the more EXACT you can be with your answers, the better):
After reviewing each section of this recent CAT, how many questions did you get wrong....
1) Because of a silly/little mistake?
2) Because there was some math/verbal that you just could not remember how to do?
3) Because the question was too hard?
4) Because you were low on time and had to guess?
5) How many Verbal questions did you 'narrow down to 2 choices' but still get wrong?
GMAT assassins aren't born, they're made,
Rich