In this case you do not need to pay any other fee other than registration fee for csab which is non refundable  and you can sit in csab if you get a seat in round 1 then also you need not to pay any seat acceptance fee and you can either accept your seat, withdraw or participate in 2nd round but iin 2nd round the seat will be binding to you and you will not get any fee refunded if you do not take admission after round 2 but if you withdraw from round 1 you will get the refund also if you do not get any seat in csab then your josaa seat will prevail