Re: 1 vary stupid scope question and 1 not so stupid
Scopes adjust by changing the angle between the line of sight and the bore.
If your scope is dialing 1/4 MOA, then your point of impact moves 0.2618 inches per click.
At 200 yards, it's twice that.
At 300 yards, it's three times that. And so on.
Since, as has already been noted, a 0.1 mil click at 100 yards moves the point of impact 0.36 inches, a 0.1 mil click is less precise than a 1/4 MOA click.
People choose that value because (a) their reticle is in mils, and it's advantageous to have the reticle and the adjustments in the same system, and (b) because it takes more 0.25 clicks to adjust to a new distance, which many think a handicap when they are in a hurry.