Hi lsmith01t,
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, 4 of your 5 recent CAT score results show that you essentially performed the same each time (about 620 +/- a few points). The 680/Q46 is a significant 'outlier' (you were averaging in the high Q30s, but jumped to a Q46 in just one week; that doesn't seem like a realistic improvement in such a short period of time).
Since the GMAC CATs are arguably the most realistic CATs available, it would make sense to do a full review of that CAT (with the goal of trying to define WHY you got questions wrong). Your Verbal performances have been consistently strong, so we can focus on the Quant section for now.
After reviewing the Quant section, how many questions did you get wrong....
1) Because of a silly/little mistake?
2) Because there was some math 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?
GMAT assassins aren't born, they're made,
Rich