I knew that there was 1/4 " and 1/8", I did not know about 1/10 mil clicks. Does this type of adjustment have a specific purpose or is it just personal preference?
Oh I don't know about a specific purpose, except to move the reticle.
In MOA scopes, I've heard of 1, 1/2, 1/3, 1/4, and 1/8 clicks. Then you've got the IPHY-adjusted scopes, with most of the same increments. Then the .1 and .05 mil scopes. Obviously the larger (1, 1/2 MOA) adjustments are better suited for some tasks and the smaller (1/8 MOA, .05mrad) adjustments are better suited for others (i.e. benchrest).
I think 1/4 MOA, 1/4 IPHY, and .1mrad have become the most popular because they're a good balance between precision and minimizing the number of clicks required. The 1 MOA scopes are harder to adjust just where you want them, and the 1/8 MOA scopes require a whole lotta clicks to shoot way out there.
Well, I'm done babbling.