Overpayment letter from the unemployment office

The agency says I reported earnings incorrectly, but I think I followed the instructions. Thank you in advance. I did not notice any errors at the time. Has anyone disputed one of these?

If you are unsure, free legal aid in your area may help for this kind of notice.

Thanks for writing this out. I went through something close to it 9 months ago, and it settled down once I kept a simple log of every call and form.