If you accidentally use an MSKU that has already been assigned to a different ASIN in your Unlisted Inventory, InventoryLab will automatically add _1 to the end of the MSKU in your Unlisted Inventory to prevent issues with duplicate MSKUs.
For example, let's say I entered MSKU 3350Test_1 for an item I listed directly in Seller Central.
Since I listed the item directly in Seller Central, I forgot that I had already used this MSKU for a different ASIN in my Unlisted Inventory. In this case, if I tried to add the Unlisted Inventory item to a batch in Stratify, I would receive an error since the MSKU has already been assigned to a different ASIN in my inventory.
To prevent this, InventoryLab will automatically add _1 to the end of the MSKU in my Unlisted Inventory. Here you can see that the MSKU has changed to 3350Test_1_1:
Now, when I am ready to add the item to a batch, I won't receive an error since it has a unique MSKU.
When this happens, a notification will appear in Stratify to let you know that an Unlisted Inventory MSKU has been updated. Clicking the link in the message will take you to the item in your Unlisted Inventory for review.
InventoryLab checks for duplicate MSKUs caused by this scenario once per day.