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

I picked up part-time shifts as a customer-service rep and I am confused about how to report them. I would rather hear the honest version than the polite one. Pay posts on a different day from when I work. Who can I ask without risking my claim?

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