You probably don't need to amend your return at all since the IRS caught the mistake. Here is what they say about when to amend and return and when not to:
https://www.irs.gov/taxtopics/tc308
If you discover an error after filing your return, you may need to amend your return. The IRS may correct mathematical or clerical errors on a return and may accept returns without certain required forms or schedules. In these instances, there's no need to amend your return. However, do file an amended return if there's a change in your filing status, income, deductions, or credits. Use Form 1040-X, Amended U.S. Individual Income Tax Return (PDF) to correct a previously filed Form 1040 (PDF), Form 1040A (PDF), Form 1040EZ (PDF), Form 1040-NR (PDF), Form 1040-NR-EZ (PDF), or to change amounts previously adjusted by the IRS. You can also use Form 1040-X to make a claim for a carryback due to a loss or unused credit; however, you may also be able to use Form 1045, Application for Tentative Refund (PDF) instead of Form 1040-X. Also, if the Form 8938, Statement of Specified Foreign Financial Assets (PDF) applies to you, file it with an annual return or an amended return. See the Instructions for Form 8938 (PDF) for more information.
If you decide you need to amend your return, make sure you start your amended return from the original return as it was filed. After starting the amended return, make sure you enter the correct refund as received from the IRS after they adjusted your refund.
