Hi,
That is really a question with no single answer; as the magnification is normally dictated by the environment..specifically the mirage.
On cool environments with open terrain you will choose a different magnification than on a hot arid environment with crowded terrain.
If I adjust my magnification without paying attention to the settings and then look at settings it typically ends up around the 22-23 power mark for my normal shooting environments.
Sincerely,
Theis