First ... do NOT amend the return before you have received the original refund !!!
Then ... Look at the form 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.
Instructions for Line 19—Amount Available To Pay Additional Tax
If line 18 is larger than line 17, line 19 will be negative. You will owe additional tax. To figure the amount owed, treat the amount on line 19 as positive and add it to the amount on line 11. Enter the result on line 20.
https://www.irs.gov/instructions/i1040x
