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The issue is caused by the date of the 1st invoice, it 's is preceding the 2nd invoice. In the above example, 1st invoice is posted on 05/12/2022, but 2nd invoice is being created on 04/12/2022 . (as per the system no sales were made before this date, therefore it 2nd invoice is not considered).
But if you create invoices subsequently, the system will show you only the remaining items and qty that have not been invoice invoiced yet based on this particular Customer Order:
Thanks for being a FIRST BIT Customer!