Told I owe money back on my benefits after 11 years as a social media manager

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?

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.