How do you report hours that vary week to week?

My hours change every week at my new part-time job and I am afraid of reporting wrongly. There are 8 people counting on me, so I am trying to be careful. Sometimes my paycheck is late by a week. 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.