EZ Inventory has 3 types of inventory updates you can choose from to update the available quantity in Shopify:

Set Available Qty

This will overwrite the inventory quantity in Shopify with the quantity from the inventory feed.

Shopify Quantity = Inventory Feed Quantity

Increase Available Qty

This will add the inventory feed quantity to the current inventory quantity in Shopify.

Shopify Quantity = Shopify Quantity + Inventory Feed Quantity

Decrease Available Qty

This will subtract the inventory feed quantity from the current inventory quantity in Shopify.

Shopify Quantity = Shopify Quantity - Inventory Feed Quantity

Please note that these will update the "Available" quantity only; we currently don't support updating the "Committed" or "On Hand" values.