What is the Difference Between My Large and Small Paintings Category?

What is the difference between my large and small paintings in my shop?  The answer is 12 inches.  If a side of the artwork is 12 inches or larger, I will put the painting in the "Large Paintings" category.  So for example, 9 x 12 inch painting goes in my large paintings; 8 x 10 inch painting goes in my Small Paintings category; 12 x 12 inch goes in large paintings, 10 x 10 inch goes in small paintings.  Hope this makes sense!