How do you report hours that vary week to week?, bookkeeper here

I picked up part-time shifts as a bookkeeper and I am confused about how to report them. There are 14 people counting on me, so I am trying to be careful. Pay posts on a different day from when I work. Do you report when you earned it or when you were paid?

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