The sp to get the cart is

CREATE PROCEDURE [dbo].[Smith_GetShoppingCart]
(
@cartCookie varchar(30)
)
AS
BEGIN
SELECT * FROM Smith_ShoppingCart where [cartCookie] = @cartCookie
END

When I look in [Smith_ShoppingCart] in the db, I have multiple lines of the same @cartCookie/productID/unit cost/sku.

How can it possibly work giving that combination? Shouldn't it delete out the original record when quantities change etc? Does it just use the highest CartID increment?