Offline stations are stations that will play in the event the internet goes down for your SoundMachine player.
To change the default offline station:
Click on the Users tab, then click "Edit Device" on the player you want to update.
A window will open and at the bottom you will find "Offline Station", pick your preferred station from the drop-down menu then click "OK" and you are set.
NOTE: When picking your offline station, make sure you leave the automatic maintenance settings in place as shown below: