Thrust quantity breaksapp dynamically creates discount codes for each campaign. You do not need create any discount code by yourself from shopify discount panel. Thrust quantity breaks will create necessary discount code using shopify's state of the art api and attach it to the campaign. We highly recommend not to edit/delete these auto generated discount codes from shopify discounts management panel. Once modified or deleted, the related quantity break will not work properly.
If you accidentally modify any of the discount code related to any offer, we highly recommend deleting the campaign and recreating it. It only takes a few minutes to setup a quantity break offer. Reversing the changes in shopify discount is also a choice but unless you are very certain about it, we do not suggest it.