Reporting part-time earnings while on benefits - 10 months and counting

I picked up part-time shifts as a delivery driver and I am confused about how to report them. There are 13 people counting on me, so I am trying to be careful. 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.