Hi aspirant,

The float option is provided to a candidate by JossA, in case if he/she has been allocated a seat in initial rounds and wants a higher preference by accepting the current one. Now when you get a seat of higher preference it depends upon you whether  you wish to upgrade your current one or not. You can still wait for further rounds and see if any more better choices are available but once all rounds are over, the seat will be locked and no changes will be made.

For more information on the topic read our article at JEE Advanced Counselling and Seat Allotment 2021 - Registration (Started), Check Dates, Process, Documents (careers360.com)

Hope it helps!!