Stimulus mistake increased my refund.

The 1040 line 30 stimulus claims $3,600 if you don't fill in anything.  The claim is the default ! Anyway I filed yesterday, and instead of a $4000 refund I erroneously claimed $7,600...  Turbo will not let me proceed with an an amended form saying it isn't ready yet. If I get a $7600 refund I will repay the $3600 same day as a 2020 tax payment. But what paperwork do I need to do ?  I think defaulting to claiming a refund with no positive input required,  is dangerous..