First of all, did you have the fees deducted from your? That might leave a 4200 difference. Which could be the Recovery Rebate Credit on line 30 for 3 people. Are you married with 1 dependent?
EIP3 The 3rd Stimulus payment started going out in March 2021 and is for 1,400 for each person listed on your tax return, no age limit. The IRS used your 2020 (or 2019) return to send the checks out fast. If your 2021 return changes and you qualify for more you can claim the extra as the Recovery Rebate Credit on 1040 line 30. But line 30 is only if you didn't get the full amount or qualify for more. Not the amount you already got. The IRS also sent out letter 6475 to tell you how much they sent you . If you are married then each spouse should get a letter for half.
When you fill out Turbo Tax it starts out by giving you the full amount you qualify for. Then at the end you enter how much you already got so you don't get it again. A lot of people forgot they got the deposit last March - May. Or missed one payment and entered the wrong amount. Then when the IRS reduces their refund and they check their bank accounts they have been finding the payments.
So Double check your bank statements and Check your IRS account (both accounts if married)
Your Online Account | Internal Revenue Service
