Devices

When NebulaAuth logs into an account as a mobile device, Steam sees a phone model. The Devices tab sets the list of models NebulaAuth chooses from.
How a model is assigned
An account gets a random model from the list at its first login in NebulaAuth. After that, the model does not change: it is saved in the maFile.
When you export maFiles, keep Device checked. Without it, the account gets a new model after the maFile is imported again.