Automatic zoom

Hi,
1) I have a question about: "Automatic zoom",
for each preset (cycling or hiking - other).
And now:
speed 0.0 >> magnification 30
speed 10.0 >> magnification 90
do I understand correctly: from 0 to 10 km / h the magnification will change smoothly from 30 to 90?

2) Why do we have 0, 30, 90, 200, 400 magnifications - and you cannot enter 100 or 300?

3) In the cycling preset I also have the option: "Enlarge all maps" = 600%.
when does point 3 work and when does point 2 work?

waldek