If you enable Shopify to track your inventory, then make sure that you understand how items are counted and tracked when you receive them from the supplier. The number of incoming items varies based on the items that you’ve received (regardless of whether you mark them as Accepted or Rejected).
For an example, suppose that you have a transfer with 10 items.
If you ordered 10 items, received 7 of them, and marked 4 as Accepted and 3 as Rejected, then there will be 3 incoming items for that product. This is because you've indicated that although 3 of the items that you received weren't in the condition that you expected (the 3 that you marked as Rejected), you still received 7 of the items that you ordered.