While giving cat mocks what should I compare percentile or marks.I am preparing for IIM.
Well you are scoring decently well.
However, just a word of caution, if you are a GEM (General, Engineer, Male) you need to improve your scores and try to obtain at least 160-180.
Because for such a category, you can target no less than 99 percentile.
Comparisons and evaluation must be done based on scores in mock tests /simcats because your percentile in such tests is based on several things, the number of students giving the same test though in different time slots, averaged out scores of the past simcat results, computational results. Anyway, this isn't of any huge concern for you currently.
As a potential candidate for IIMs, focus only on your scores because even in the main exam of CAT, you will never know what kind of students will appear, what would be the average score to achieve to cross 98 percentile, what would be slot, etc because everything is just to comparative.
However, if you focus solely on achieving a good score, no matter what others have done, you will stand a strong chance of getting a high percentile.
My last piece of advice: if a gem student , target 180+ now as well in main SIMCAT
If a category student, target 150+
If an academic diverse student, target 110+
(These are solely based on past records, nothing to do with the confirmed cut-off scores).
All the best!!