get Form 1040-X from the IRS Website in fillable PDF. check the box for 2021.
copy Col C from the amendment you filed into Col A and Col C.
Col B will be zero.
Fill out Lines 16-22.
Leave Line 23 empty.
In explanation, write
"This is amendment No.2 for 2021"
"I paid 1040-X No.1 amount you owe of $nnn twice"
your refund lines 21,22 should be $nnn.
@Bleary Eyed
