Anyone familiar with IRS process for receiving a penalty refund?

ruouttaurmind thought this was worth mentioning said

In March, 2020 IRS incorrectly billed my business for a late filing penalty and interest (a bit over $1,900) for my 2018 form 1120 return. Knowing that the wheels grind slowly in the IRS, I immediately paid the penalty and interest, then wrote a response which included my proof that the penalty was not justified. In December IRS wrote back indicating they had received my response, but would need more time to investigate.

Finally, today I received a letter from IRS that my “request to be granted penalty relief” was approved.

I already paid the penalty. So how do I get that money back? The letter from IRS has no instruction on how to proceed, and makes no statement about where my payment went.

I tried a search of the interwebs, but once you type in those three letters (IRS) all hell breaks loose and you get buried with tens of millions of results.

Anyone here have any experience with this?