Got an overpayment notice, what now? (Richmond)

The agency says I reported earnings incorrectly, but I think I followed the instructions. There are 18 people counting on me, so I am trying to be careful. I did not notice any errors at the time. Has anyone disputed one of these?

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