Overpayment letter from the unemployment office after 15 years as a school bus driver

I received a letter saying I was overpaid about $700 on my claim. I have read a lot of threads here and could not find my exact situation. I did not notice any errors at the time. Has anyone disputed one of these?

Collect your pay stubs and certification records for the weeks they name. Mine showed the error was a date mix-up.