The 4 speed is simply an Atlas 2 speed case with a planetary gearset in front. The planetary is always 2.72:1. You select the ratio in the main case, and the combination of the two is what creates the 4 speeds.
2 shifters control the main case - exactly like a 2 speed - and a 3rd shifter controls the planetary.
Doesn't add as much as I expected to the price, they give you a decent deal for it being already filled with gears vs the doublers by themselves. I did think it would be way more