A = Auto
M = Manual
It's an early version of steptronic .. sorta.
If you put it in M and drop the shifter to 1 (might start at 2) then you won't be able to shift out of that gear until you move the shifter up. Likewise, if you put it in 3, you'll be in 3rd gear.
If you put it in A and drop the shifter to .. say 3. It'll start in 1st and shift up, but will not go any higher than 3rd gear.
Member of the First 5 Uniters.