Products are linked to 'Inventory Stock to Use' on the General tab of the Product Profile under the CheckOut section. Consider adding a field of the current inventory value, of the value selected in 'Invnetory Stock to Use'. Otherwise you ahve to toggle to the Inventory section to get the current inventory level.
Or in a grander scope, move the Inventory values into the product profile set-up under a category call Inventory instead of the current CheckOut category.