Your 2021 return starts out by assuming you didn't get any Stimulus payments so it gives you credit for the full amount and your refund was too high. Then near the end you enter how much you actually got so it only gives you the difference if any. So you don't get it again.
Look at your tax return. It is not added as income anywhere or subtracted anywhere. The Recovery rebate credit on line 30 is only if you didn't get the Stimulus payment or qualify for more.
