I learned a long time ago back when my 323i was an automatic steptronic before I modified it to a manual transmission that the computer did a TON better job shifting the automatic than I could do.
This is two fold.
One it can jump more gears than you can since it can go from 5th to 1st if it wants to. You cant.
You can go from 5th to 4th and then 3rd etc.
But you cant go from 5th to 1st.
So this simple formula means that you cannot EVER shift as fast as the computer can.
I know you think you can.
But you can't.
So the best positions for that shift is as follows.
P for park
R for going backwards
D for driving forward
Anything else and your hurting performance