what he means is, how are you determinin that the particular rocker that you are adjusting is at the base circle portion of the cam rotation?
if the rocker you are adjusting is on a lifter that is starting to come up, or not all the way down yet, you will end up with either too little preload or even some lash.
I usually only set the preload by turning the engine over by hand on a motor that is being put together. If the engine runs, I just run it with the valve covers off, and adjust them running.
How to adjust hydraulic lifter preload for a stock type lifter(not an anti-pump up):
run the engine with the v/c's off, try to use rags where the oil is squirting to, or put a piece of cardboard up across the outside of the valve cover flange.
most likeley, it will still be messy.
on a chevy, I use 1/2 a turn of preload, so I back off the adjuster nut till I can hear it making noise, then tighten till the noise stops, then turn it another 1/2 turn, repeat 15 times.
I looked to find out how many turns it will take to achieve the proper preload but chrysler does not list one since they aren't adjustable stock, they do list the dry lash though, which is the type of spec used when adjusting an anti-pump up lifter. the spec is .060-.210. this is measured from the point where the lifter bottoms out to your final position.
if you are going to do this turning the engine by hand:
you turn the engine till the valve you are working on is at bdc(tdc of the piston compression strokeis close enough)
slowly crank down the lifter while giving it time to collapse bleeding off the oil. it is best to do this if the intake is off, but you can peek down the pushrod opening sometimes. each time you turn it a few turns and stop the valve will open slightly if the lifters don't bleed very easily, then you wait till the valve closes and turn it some more. you can start off with more at a time, then as you get close to the bottom slow down. It,s allright to go a little too far, but be gentle.
When the lifter cup is all the way down you will turn on the adjuster, avalve will open slightly, and not slowly go back closed.
at this point, back off very slowly till the valve just closes again, then back off the number of turns that equals the specification.
to do this kind while engine is running, just tighten adjuster till you can hear a misfire, then wait for it to subside as the oil goes out of the lifter, until the misfire remains constant, then back off the specified amount.