Reporting part-time earnings while on benefits - what worked for you?

I picked up part-time shifts as an accounts payable clerk and I am confused about how to report them. It has been a long 5 weeks. The form asks for gross earnings, which I do not see until later. Who can I ask without risking my claim?

I estimated and then checked my pay stub. When there was a small difference I wrote to the agency to correct it.