How do you report hours that vary week to week? after 17 years as an IT help-desk technician

I picked up part-time shifts as an IT help-desk technician and I am confused about how to report them. I would rather hear the honest version than the polite one. Pay posts on a different day from when I work. Who can I ask without risking my claim?

Thanks for writing this out. I went through something close to it 6 months ago, and it got easier once I kept a simple log of every call and form.