Hello dear

If you don't want to accept the seat offered to you, you can still wait for the further rounds. All you need to do is choose the option of float, so that you may get another college which was there in the list filled up by you. Or if you want the same college, you can choose the slide option. If you do not want to go ahead, then you may simply drop out of it, you won't be considered for further counselling. It is all up to you.
I hope this helps. Regards.