Hello student I request you to please help me with the examination counselling you're concerned about so that I can check and provide you the exact information also help me why you want to change your subject from mathematics to Biology.

If you've both the subjects in class 12 and the eligibility criteria says you need biology/mathematics then there's no need to change the subject the counsellor will automatically count your eligible subjects for further process.

Feel free to comment if you have you have any doubt

Good luck