Good question - the idea was the main product is the # in stock of the main product. The # in stock on the option are for any accessories/versions. Let me give you an example:
A listing is for 10 widgets. The num in stock for the product is 10.
However some come with cases, and there are 5 cases in stock. So the # in stock on the option would be 5.
Each option includes the main product and that is where we determine if a product is or isn’t sold out. Make a bit more sense?