Hi. Congratulations on securing a seat in IIIT, BBSR. So coming back to the question, now you have to pay the fees for IIIT. Its termed as partial admission fees. If you want to apply for the CSAB counseling then don't fill the institute's registration form. Fill the CSAB form which will begin from tomorrow. And if you don't get a seat in spot round then your seat will still be there. Your allotted seat of IIIT will be cancelled if and only if you get a seat in CSAB counseling. The  money will be adjusted in the new college you get in through CSAB. Don't worry about it.

Hope this helps.