Actually you shouldn't mail the amended return until you get the first original refund. Was the first one accepted?
IF YOU HAVE FILED:
You first need to wait until the IRS Accepts or Rejects your return. If they reject it for some reason you can just fix it and resend it.
If it was Accepted, you need to wait for your return to be fully processed and you get the first refund or your tax due payment has cleared. Then you can mail in an amended return. Do NOT change anything yet on your return until you start the amended return. If you have changed it then take out the changes and put it back to the way it was when you originally filed.
How to Amend
https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed You will still get your original refund or need to tax the first tax due. Then the amended return will only be for the difference you get back or need to pay back. The Amended return will take up to 16 weeks to process and they only mail checks for refunds.
The amended return will only show the difference you get back or need to pay. You can confirm this by printing your amendment and looking at the 1040X. Line 18 should be your original refund amount and line 21 should be your additional refund. If you paid on your original return it will be on line 16. If there is an amount owed with the amendment, it will be on line 20. When you go through the amendment section it asks you how much you paid or got back on the original return so be sure to enter it. You might need to go back and answer that question. I think it's one of the last questions in the amended section.
