Hello aarsh,

There are three options given by josaa to candidates and they are

Freeze – Candidate is content with the allocated seat and pays the seat
acceptance fee. This candidate is not interested in participating in
further rounds of seat allotment and hence will not be considered in subsequent
rounds.

Float – Candidate accepts the allocated seat, but will wait if a
better seat ( in any institute ) of his/her preference is offered in
subsequent rounds. If not, the candidate can always go back to the previously
allotted seat.

Slide – Candidate accepts the seat but will wait if a better branch ( in the
same institute ) of his/her preference is offered in subsequent rounds. If
not, the candidate can always go back to the previously allotted seat.

So if you have gone by choosing float then you can get upgraded choice in round 2.