Told I owe money back on my benefits (Nashville)

The agency says I reported earnings incorrectly, but I think I followed the instructions. This is my first time dealing with any of this. I did not notice any errors at the time. Has anyone disputed one of these?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.

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