Hello Harsh,

No need to worry about that if you have alotted a seat in a college which you dont like in the first round then are left with 2 options,You can either cancel you seat by selecting reject option(or any other similar options) or you can select float option to keep that seat as a last choice and move forward. by selecting any of the options among the 2  you can move forward in round 2.you can always move to further rounds until you select freeze option.

hope this may help you.