2 attributes 1 product

I have a product with two attributes, each with its own assigned stock quantity:

• Attribute1 – 3 qty
• Attribute2 – 1 qty

When a product is sold, does the quantity for each attribute decrease accordingly? For example, from 3:1 to 2:0? I’ve noticed that when one of the two attributes runs out of stock, the product displays as “Out of Stock” online, even though there is still stock available for the other attribute. Why does this happen? Is it possible for these two attributes to share the same stock so the product remains listed as “In Stock”? I hope this makes sense.