IRS Letter 3064C

Received a 3064C in the mail the other day from the IRS. I've been waiting on my return since January. The letter doesn't ask for any document(s) in particular. It simply says:

 

"Dear Taxpayer,

 

Thank you for your correspondence 02/27/20. Your correspondence was received and applied to your Dec. 31, 2019 account."

 

Then it just gives me a number to call, which I can't get ahold of anyone on, in case I have questions. Anyone receive one of these? Any idea what it means?