You needed to enter the total amount you received for the 3rd Stimulus payment. Line 30 is only if you didn't get the full amount or qualify for more.
Did you see these screens when you filled out your return? See Critter's screen shots
https://ttlc.intuit.com/community/after-you-file/discussion/irs-notice-error-in-2021-form-1040/00/27...
