When your inventory arrives, you can use a transfer to make sure that you receive everything you are expecting. When you confirm that you’ve received an item on your transfer, it updates the number of items on your Inventory page.
Make sure that you've enabled inventory tracking for your products and variants.
To receive inventory:
From your Shopify admin, go to Products > Transfers.
Click the transfer number to open it:
Click Receive items.
For each item, click All or enter the number of items that you’ve received in the Accept column.
...button and enter the number of damaged items that you need to reject (damaged items, for example) or cancel. The quantity of the items will adjust accordingly:
When you’re finished receiving inventory (completely or partially), click Update inventory.
To finish the transfer, click Archive. Only transfers that have a Completed status can be archived.
You can see all Pending (open), Partial, Completed, and archived (grayed out Completed status) transfers on the Transfers page. If you need to update a transfer at a later time, you can click on its transfer number.
Make sure you understand how Shopify calculates incoming inventory.