A story doesn't have a height, only a layer does. A story is just a level you set and can have other levels attached to it, each with a level type. You need to look those story and level types as just key levels (= z values) that objects can bound to. When you then change a level, objects will follow. The thing with VW is that for defining a level, you have to make a layer, and the z-height of that layer is the level. Apart from all those levels, layers also have a height, which you can use separately to also bound to. A good setup of stories and layers will result in an easy workflow where things are easy and quick to adjust, but you have to think it through and experience which way works best for you.