How do you report hours that vary week to week? - 11 months and counting

I work some days through a staffing agency while still certifying. Sometimes my paycheck is late by a week. 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.

The claimant handbook has worked examples for part-time pay. Mine was clearer than the phone line.