Look at the 1040X very carefully .... if you have not yet sent in any payments make VERY sure that line 16 is a zero ... if it is not then change it to a zero and recompute lines 19 - 22 to see if you do indeed have a refund or just owe less.
If you just owe less then send that payment with the 1040X ( no voucher needed) and expect a letter from the IRS saying you didn't pay all of the original balance due ... this will resolve itself as the process the amended return which can take weeks.
If you really do have a refund on line 22 then you don't need to make any payments.
Review the entire 1040X....
Column A should have the figures from the original return, Column C the corrected figures and Column B the differences between the other 2 which needs an explanation on page 2 of the form 1040X.
If you completed it correctly you will see an entry on either line 16 OR 18:
On line 16 should be the amount you paid with your original return.
On line 18 should be the amount of your original refund you received.
Then you will see your extra refund on line 22 OR the new balance due you need to pay on line 20.