Did you check each of your IRS accounts? Each spouse should show half. How much were both the 6475 letters? Were they each 1400 or 2800 or 2100 or ? If your account shows 2800 then maybe your spouse's account also shows another 2800 or 1400.
How many people were on your 2020 return? Did you change the number of dependents on 2021? Like add a new child or delete a dependent? Maybe you replaced a dependent with another dependent so you had the same # of people?
