Those aren't different instructions. Those are different built-in rocker geometry (the angles between the ball center and each arm). Miller says "smallest path" because he has the mid-lift patent, which produces the smallest possible scrub.
Normally, an engine with restricted breathing and shrouded valves (chamber wall is too close) uses mid-lift unless you have some reason not to. If HS does not incorporate this, you will only be able to get mid-lift on the valve side (pushrod geo is less important). For mid-lift adjustment and pushrod measurement, the rocker tip begins closest to the rocker stud with valve closed, proceeds away from the stud and is ideally centered on the stem (not critical) at 25% lift, continues away and reaches 50% at the farthest point away (rocker is now 90° angle to the stem) and reverses. On the return trip, everything repeats backwards: 75% lift at stem center, full lift at the same (closest) point to the stud.
A BBC rocker is about 1.65" long (valve side), the scrub path at mid-lift for a .600" cam is about .027". If the geo is wrong, this distance will be both larger and asymmetrical.
