It means walk in that direction until the you hit an edge of a screen, and then the screen changes (the screen fades out and re-positions Duncan) when you walk off of it. For example: W, W, E, N would mean walk left until the screen changes, walk left again until the screen changes, walk right (yes, this means heading exactly back where you came from, it's tricky!

) and then walk up one screen. Does that help a little?