Hello!
Your admission through NATA is based on your merit system. Divide the NATA score by 4, and your CBSE result by 2, and add them to find your merit out of 100. Normally colleges accept a student who has 60+ merit overall, and sometimes colleges even go for lower merit. The cut off for Manipal changes every year, so previous trends cannot be trusted fully in Manipal's case.

Good luck!