There are other folders (Segments, Composites, Elements) that contain structure definitions for those EDI components. You should never need to use these directly as everything required is present in the transaction structure. They are provided because the specification metadata is created exactly it is specified by the EDI standard. You may also note that in the transaction structure some elements show the change indication icon (a small gold triangle in the icon). This represents the cases where the definition in the transaction specification overrides or augments that of the underlying segment/composite/element. Again, no action on your part is required, this is just for information.