If an inventory item has 0 quantity , how can it have a negative or positive ASSET VALUE

I'll share the details you need about the asset value of your inventory item, @jennifer48. An inventory item that has zero quantity will have a negative value when you create an invoice to sell it. On the other hand, it'll have a positive value when you create an expense for this item and enter quantity more than what's on hand.

For future reference, check out this article: Set Up and Track Your Stock. You'll find steps on how to turn on stock tracking, add your products, sell, restock them, and run inventory reports. 

Let me know if you have additional questions, @jennifer48. I'm always around to help you some more.