Symptom

The set coordinate system (i.e. some projected coordinate system) does not match the network objects' coordinate values (i.e. meeting a geographic coordinate system, thus showing degree values).
How can I solve this?

Cause

In
Network -> Network settings -> Scale -> Coordinate system
the declared coordinate system can have been set but that can be wrong.
Or the coordinate system "Visum" means that no coordinate system was declared at all.

Resolution

Choose the correct coordinate system, for example WGS84:
Geographic Coordinate Systems -> World -> WGS 1984.

Klick OK and uncheck the option "Transform coordinates in case of changes".
This will declare the coordinate system to meet the correct network object coordinates.