How do you report hours that vary week to week? - first time posting

I picked up part-time shifts as a software tester and I am confused about how to report them. I have read a lot of threads here and could not find my exact situation. Pay posts on a different day from when I work. Who can I ask without risking my claim?

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