auto tranny

i asked a few months ago but didnt get an answer. Ill ask again.
91 MM auto tranny. Im only counting 3 gears when driving, been like this since we got it last year. shifts nice and stiff, no slip no noise. i thought these were 4 speed tranny. when i gun it, the kickdown kicks in fine.
the question.... 3 speed or 4 speed.

when where counting did you count 3 shifts if that was the case you do have a 4 speed starts out in one gear and shifts to 3 more