Hi anmkgmat2018,
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, 3 of your last 4 CAT score results show that you essentially performed the same each time (about 600 +/- a few points). The 680 is an 'outlier', so it's not clear how indicative that Score is of your current ability level. Raising a 600 to a 700+ will likely require at least another 2 months of consistent, guided study. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level. However, with just 20 days of potential study time, the goal to improve 100+ points might be too difficult to be considered realistic.
Before I can offer you the specific advice that you're looking for, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How long have you studied?
2) What study materials have you used so far?
3) Have you taken any CATs besides these 4 CATs? How have you scored on EACH of those other CATs (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
4) When are you planning to apply to Business School?
5) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich
