which Table used for to Billable Utilization
Go to the customize form and check the table name.
can you elaborate more because i cant find anything related to table or my exact scenario is in Billable Utilization there is column total billable hours so their if the value is null it is showing blank but i need to set the default value as 0.00
which doctype, which table, is it custom doctype? please share the usecase with the screenshot.
From what you said I understood that you were looking for a table name 
in Billable Utilization Total Billable Hours is showing blank as it was coming as null but instead of showing blank i need to show 0.00
It’s your custom report, erpnext does not provide a Billable Utilization report. So contact whoever developed this report.