It is the name sent to an automation system.
AL-0 is AquaRite and is the normal setting for units without automation.
AL-1 NatureSoft
AL-2 MineralSprings
AL-3 SmartPure
AL-4 This changes the default display from average salt to percent output.
AL-5 This is used with Jandy automation.
I think that aquarite, naturesoft, mineralsprings and smartpure are essentially the same unit with different branding. They do private labels for certain companies. I think that al-0 to al-3 are basically equivalent other than a superficial name change. AL-4 is not about the name, it just changes the default display. I think that AL-5 needs to be selected for the Jandy automation to control the unit properly.