Reporting part-time earnings while on benefits - what worked for you?

I picked up part-time shifts as a graphic designer and I am confused about how to report them. I do not usually post, so bear with me. The form asks for gross earnings, which I do not see until later. Who can I ask without risking my claim?

Thanks for writing this out. I went through something close to it 12 months ago, and it got easier once I kept a simple log of every call and form.