What do you mean with watershed? I wasn't shure, if I translated it correctly, so I checked the dictionary. Watershed means, were two rivers melt into one (or where a river splits), for example.

What does it mean with this trainstation???

Please help me to understand, what you mean, because the issue you have might concern me as well... Thanks!

What he means is the area that the station covers without the need for additional transportation connections -- like a bus route. This mod doesn't show if an area is connected to the station -- white for when you want to connect to an industry. Hope that helps...

Build the station with "connecting roads" enabled.
Place a road next to it and the catchment area will show the same as vanilla stations