How do you report hours that vary week to week? - what worked for you?

I picked up part-time shifts as a welding apprentice and I am confused about how to report them. The form asks for gross earnings, which I do not see until later. Did anyone get an overpayment notice from a mistake?

The claimant handbook has worked examples for part-time pay. Mine was clearer than the phone line.

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