Combine Like Ingredients (Shopping List)

When I use Combine Like Ingredients in the shopping list it doesn't appear to work. Why?

Combine Like Ingredients will combine ingredients by the same name and unit of measure. For example, create a new shopping list. Type these two things:

butter, 1 cup
butter, 1 tablespoon

Press the Combine Like Ingredients. It combines them. It combines like volume measures (tablespoon, cup, etc.) It combines like weight measures (ounce, pound, etc.) It cannot combine volume and weight because those are two different types of measurements.

Furthermore, computers are very literal. So if you have melted butter as an ingredient it won't combine it with butter. They are two different things to a computer.

Therefore, if you want to combine like ingredients, they need to be "like" in order for it to work properly.