How do you report hours that vary week to week? after 4 years as a dental hygienist

I work some days through a staffing agency while still certifying. The form asks for gross earnings, which I do not see until later.

Thanks for writing this out. I went through something close to it 14 months ago, and it got easier once I kept a simple log of every call and form.

I estimated and then checked my pay stub. When there was a small difference I wrote to the agency to correct it.