Select the application that you use for inventory management. The inventory and stock information in the Inventory Master is used to override the other location.
If you choose Shopify, the inventory information (Quantity on Hand) in QuickBooks is overwritten with values that of Shopify.
If you choose QuickBooks Online, the inventory information (Quantity on Hand) in Shopify is overwritten with values that of QuickBooks Online.
Note: It is advisable to choose QuickBooks Online as the Inventory Master when you sell your product through multiple channels or you have created your product in QuickBooks Online first or maintain purchase orders in QuickBooks Online, else choose Shopify as your Inventory Master.