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: