To create the sweetness scale that can be used to gauge the relative intensity of sweetness of various ingredients, the taste of various sweeteners is compared to table sugar (sucrose). The less sweet a substance, the lower its value. Most sugar substitutes, whether natural like stevia or artificial like sucralose, are extremely sweet when compared to table sugar.
Keep in mind that many of the sweeteners listed in the table here are sold in a solid or liquid form and can behave differently in recipes for cakes and ice creams, and several sweeteners like lactose, honey, maple syrup, molasses, and agave have their own intrinsic aromas and tastes, which will affect the final flavor of the food.