How do you report hours that vary week to week? (update)

My hours change every week at my new part-time job and I am afraid of reporting wrongly. Sometimes my paycheck is late by a week. 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.

Keep everything in writing and save the confirmation numbers. It saved me later.