Wage reporting when hours change weekly (update)

I picked up part-time shifts as a graphic designer and I am confused about how to report them. The form asks for gross earnings, which I do not see until later. Do you report when you earned it or when you were paid?

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.