Dear student,

If you got allotted any seat in josaa counselling, then you can participate in csab counseling by retaining your seat.
Now if you got allotted any seat in josaa round 1 counseling, then pay the fees, and accept it.
Now if you want to participate in csab round counseling, then you have to again pay a fees of rs. 36500 and then if you accept your seat in csab round counseling, then your josaa seat will be cancelled anyways. Also you can withdraw your seat before participation.

Also check out the following link to know more about csab 2020 counseling :-
https://engineering.careers360.com/articles/csab-special-round-for-nits-iiits-and-gftis