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

I picked up part-time shifts as a barista and I am confused about how to report them. Pay posts on a different day from when I work. Do you report when you earned it or when you were paid?

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

Thanks for writing this out. I went through something close to it 2 months ago, and it got easier once I kept a simple log of every call and form.