Apart from editing remains directly when editing a product, they can also be managed on an extra page that can be found in the upper menu bar of the website control panel using the following path:
Applications -> miniShop2 -> Remains.
The table displays all entries from the remains table. So you can also find here combinations of properties that are no longer valid. Such entries can be removed from the table unless they are needed.
To edit remains, double-click the left mouse button on the number you want to change. Then a field for entering remains amounts will appear. Input a new remains amount, press Enter, and the new amount of remains will be saved in the database.