Hi,
Welcome, and thanks for joining the forums!
The product master does not do what you mention exactly... the purpose of it is to track the details of that item such as the cost to purchase each, etc.
The active listing tab can track the quantity of inventory you have unsold, and the sold item tab can track the quantity of inventory that has sold.
These combined should be your total inventory for the year.
Let me know if you have any further questions about this topic.
thanks,
Scott