The idea
list-style is the shorthand for list-style-type, list-style-position, and list-style-image in one declaration: list-style: type position image. Any part you leave out resets to its initial value, so list-style: square inside sets the type and position and clears any image.
This level needs the list-style shorthand itself — the longhands list-style-type and list-style-position will not satisfy it.