JAMIA has 45 total seats for BSc Math. So as per the reservation policy of the 2020-21 prospectus, Approximately 20 seats are unresearved.

You can visit the page number 31 of the prospectus PDF following the link below in order to read the reservation policies:

http://jmicoe.in/pdf19/FINAL_JMI_PROSPECTUS_2020_NEW.pdf

I hope my answer helps. All the very best for your future endeavors!