2021 Tax Return - IRS Letter claiming underpaid - Recovery Rebate Credit Error

I submitted my 2021 taxes using Turbotax and entered that per the 6475 letter we received $1,400. Since we were eligible to have received $2,800 Turbotax used the remaining $1,400 as a credit on taxes owed. Yesterday I received a letter from the IRS saying there was an error in the Recovery Rebate Credit and that we owe $1,400. No further explanation.

 

Have you seen that before? Is our best recourse to call the IRS? Aside from that, they agree with all other numbers.

 

Thanks