If you only have your graduation marksheet and not the provisional/degree certificate yet, you can usually enter the marksheet number in the field asking for certificate number. However, since BPSC CCE form specifically mentions “certificate number,” the safest step is to either (a) contact your university to quickly issue a provisional certificate, or (b) check BPSC’s official guidelines/helpline for confirmation. Filling a wrong detail may create issues later during verification, so clarification is important.