curious about valve lash setting/check

Get the cam to its base circle using whatever method you want, MP decal, degrees or logical crank rotation looking at the opposite rocker. Spin the pushrod, and start cranking down the adjuster-you'll feel it drag when it touches the pushrod. From there, add your preload, or subtract lash on a mechanical. The TPI on an adjuster is 20 so 1 turn more is about .050 and fractions there of. Thats about in the middle of the preload range. The cup in a hydraulic rocker can compress .00x before its check valve closes and it becomes 'solid' That where the preload comes in. It gets the piston past its spring pressure into the check valve.