Wage reporting when hours change weekly - any advice?

My hours change every week at my new part-time job and I am afraid of reporting wrongly. Thank you in advance. The form asks for gross earnings, which I do not see until later. Did anyone get an overpayment notice from a mistake?

Report honestly and keep your stubs. An honest small error is much easier to fix than a missing report.

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