Title says it all. Basically we missed an estimated tax payment in the return data, and the IRS also made another small adjustment (~$15), so the IRS is sending an additional refund, but instructed us to not re-file anything. I don't see a way to tell Proconnect to make changes without filing an amendment, e.g. assure Proconnect that the IRS already knows.

CP24 notice on IRS site: https://www.irs.gov/individuals/understanding-your-cp24-notice

Curiously I find zero info about CP24 notices on the Proconnect site.