I could be wrong here but I believe that the 'Not Listed' pile of listings can be split into 2 piles:

* Products that have never been selected to be listed

* Products that have been listed but the quantity has gone to zero and so they have fallen back into the 'Not Listed' pile.

I also gather that products that are there because their quantity is zero may be automatically relisted when quantity increases.  

I think it would be helpful if these 2 different categories of 'Not Listed' products were in separate lists.