It completely depends on you. I have friends who start with us a day before and yet are 9 pointers, while we are managing 8’s.
These are very cruel souls who refuse to help people like us.
There are also people who will study day and night, everyday and still won’t score above an 8.
So come to BITS, explore, learn more about yourself and then decide how much do you need to study to maintain a CGPA more than 8,