Wage reporting when hours change weekly after 6 years as a project coordinator

I picked up part-time shifts as a project coordinator and I am confused about how to report them. There are 6 people counting on me, so I am trying to be careful. The form asks for gross earnings, which I do not see until later. Did anyone get an overpayment notice from a mistake?

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