Dear aspirant,
You can't participate in the CSAB special round without withdrawal of your allotted seat in 7th round of JOSAA counseling by reporting. If you didn't report at your allotted institute in the time of 19th July to 23rd July then your number is automatically rejected. If you want to participate in the CSAB special round 2019 then you have to report at the allotted institute. Hope it helps you.
Thank you.