I do understand the confusion.
So the "Automatic zoom correction" was something we did ourselves but did not allow the user to configure. Therefore "on" is the default behavior.
The faster you drive, the more the app zooms out.
The further away a maneuver is, the more the app zooms out.
Those factors add up 
So when driving 130 km/h on a highway while having the instruction to take the exit in 80 km means the app zooms out quite a lot.
If you drive fast in the city (70 km/h) but need to take the exit in 1km, the app still zooms out a bit to allow you to anticipate with the speed you are driving.
If you only want the app to zoom out based on speed, set it to the speed icon. If you only want to zoom out based on distance to the next instruction, put it on the instruction icon
By default it is "on" and that does both.
The baseline zoom is affected by the zoom correction. The is the normalized zoomlevel upon which all other adjustments are based. So if you want slightly less or more zoom, use that setting. This is always applied.