dear aspirant

After the first round of seat allotment, if you get a seat in any of your desired preferences, you get two options:

1.Freeze:It means you are satisfied with the seat allotted to you and you want to take the respected seat and do not wish to participate further.

2. Float: It means you are not satisfied and wish to participate in further rounds so as to get a seat in a higher preferred college and branch filled by you in your locked choices.This means that if there is vacant seat(s) in the choices above the one you are allotted and if your rank is up to the mark i.e. the seats do not get completely filled on reaching your rank, then you get a seat or else seat allotted in 1st round will be retained.After 1st round the up-gradation generally happens when a seat allotted of higher preference is not accepted by a student of higher rank and thus left vacant for further rounds.

hope it helped.