You're catching on. :-) A device simply gives you the ability to individualize hard button assignments for a group of pages, isolate a group of visible pages that you want to be able to page up and down through without paging through other visible pages, and in the case of devices which contain IR codes for example, the ability to direct those IR codes sending them as direct IR or to a given extender over WiFi.

The XM Radio device in my configuration file actually consists of 10 devices as seen in the example pics here. I use the firm keys for category selection as they allow the user to use either the hard buttons or tap the firm key labels on screen. Each category consists of two devices, one to store the (visible) channel logo pages, and another to store the keypad page. This allows for paging through the channel logo pages of each category separately. Having the keypad page in a separate device simply prevents the page up and down buttons from taking the user to the next/previous channel logo page once on the keypad page. The user must tap the keypad button again on the right side of the screen to return to the channel logo page they came from.