Letter 6475 is telling you how much the IRS already sent you. Not what you qualify for. They send letter 6475 to each spouse for half. But you need to enter the total . The 3rd Stimulus is 1400 per person, 2800 for Joint.
Double check your bank accounts and check your IRS account (both if married) to see how much the IRS sent you.
https://www.irs.gov/payments/your-online-account
