It makes numbers sequential. I also have it on my game, makes a huge difference.
If it's on (default) then numbers are random and it makes it more difficult to select it.
With the setting off then numbers are sequential: 1, 2, 3, .. so it's easier to time, if you want a 4 then you see the first 3 numbers pass and can time a bit better when to press the buttons.
Always use the fast stop button..