Dear candidate as we know, Calcutta University is one of the Prestigious Institutions of India, so here usually the marks requirement remain high. For B.Sc Mathematics you need minimum 90% marks to ensure your seat. However since you got 80.6% that too from CBSE board, your chances of admission remain low. But wait for their final list and if seats remain vacant you may get admission. By that time do search for some other good Institutions rather than relying on one college.

Hope it helps!!

Good luck!!