What a Amazon order writes
One invoice per order, in draft, in your currency.
Each Amazon order becomes one draft invoice in Xero: the buyer matched or created as a contact by name and email, one line per item at the price actually paid, and the order’s own currency. It lands as a draft so you approve it in Xero the way you approve anything else; nothing is posted to your accounts behind your back.
Amazon tells us the moment something sells, so the draft invoice is in Xero a second or so later. Cancel the order before you approve the invoice and the draft is removed. Anything you have already approved is yours to credit in Xero.
Stock Amazon ships for you (FBA) keeps its own count and never moves through this connection; only items you ship yourself are matched to a tracked Xero item.