Do NOT send in an amended return until your original tax return has been fully processed. If you try to amend and send in a 1040X before the original return has been processed, it will create confusion and delays. Do not change anything on the original return before starting the amendment process as that will make things difficult to undo. And always save a PDF of the original return for safe keeping as once you start the amendment process you will no longer have access to the original.
https://ttlc.intuit.com/questions/3318997-how-does-the-refund-math-work-on-amendments
