How much cat percntile is equal to snap percntile??

You don't need to compare the percentile of two exams in any way. Both the exams are different and are used to get admission in different colleges. As SNAP is used for Symbiosis whereas CAT which specifically focus on IIMs but has been adopted by most of the colleges a way to give admission.

Don't Judge yourself by comparing your performance on 2 exams. It's better to take them differently because as questions difficulty level, format is completely different for the two exams.

I will recommend you to first focus on CAT exam as less than 15 days are left. You need to brush up on your basics and give up lots of online mock test which will help you in overcoming your mistakes and making up a strategy to attempt the paper which will definitely improve your score and percentile.

All the best!!