Below is a copy of a post I made a few years back. See the link contained therein for more detail than Ive ever seen in any MST 100 Manual or DOD Publication:
These are the Come Ups for the Main Elevation Turret of the US Optics MST-100:
Set the Ocular first to bring the Reticle to a sharp focus against a blank background.
Adjust the objective so the scope is parallax free at 300 yards
Rough Zero the scope at 100 yards with the Main Elevation Turret set at “1”
If possible, Refine your Zero at 300 yards with the main elevation turret set at “3” with “0” on or off the vernier (Fine Tune) with whatever apparent windage is necessary.