CheckIn determines the Average Cost of a Product by taking the value of Inventory on hand, and dividing it by the quantity on hand. Note that this applies to Inventory in stock -- if you do not have an item in stock, you won't see an Average Cost.
If you have reason to believe the Average Cost for a product is incorrect, have a look through the POs for transactions for that product where the cost was entered as zero, as this may have impacted the value of inventory on hand.
If necessary, you have the option to make a manual adjustment to the total value of Inventory on hand, in the "Value" field under the "Status" tab of the Product Card.
