Hi, RW stands for Rother Wanderführer and usually the number of the hike in the book. Rother is a very popular Hiking guide in German language, and most of the trails are marked as relations.
You could also buy the Book and have access to the GPX trails on the website.
I prefer to generate relations which are displayed in waymarkedtrails.org and can be downloaded to the satnav.
There is a controversy about if trails are (to be) marked in Scotland. In Switzerland they are marked, we consider this a security feature. In Scotland, often only the start point is marked even on popular trails, some people say, there should be no waymarks, but you should use map and compass. As I contribute to Wikivoyage project, I rather provide a link to a relations with the correct trail instead of letting people to get lost in the fog and rain... Regards from Switzerland Martin
 