Reporting part-time earnings while on benefits

I work some days through a staffing agency while still certifying. This is my first time dealing with any of this. The form asks for gross earnings, which I do not see until later. 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.

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