Taff's golden rule
try and play morse code with the rocker arm while holding the tappet nut.
if you can 'just' faintly hear 'tik-tik' at the rear licence plate then they are both good.
rattling; too loose, decomp can't work.
can't hear it; undo one tappet and try it, it has to be the one you undid and if it isn't = then it is the other one!
9/10 people get 1/6th of a turn and console themselves with that "FACT". its not a fact.
you'll do well to listen!
Taffy