The area in orange was selected because the URL use to access it pointed to a specific object in OSM https://www.openstreetmap.org/way/236643480 rather than just the general area https://www.openstreetmap.org/#map=15/51.3380/-0.0381.

To get a link to an object in OSM zoom in, then click the “question mark” icon at the right and then click something on the map. For example, one of the footpaths in Selsdon Wood is https://www.openstreetmap.org/way/157473294#map=17/51.33627/-0.04844.