I don't use a 'Pushrod' checker.
I like to use the complete Valve Train intended for that engine to arrive at the 'correct' length.
I coat the top of the valve stem with a marking die (or you can use a black marker), install one lifter, one rocker and an adjustable pushrod (set to the 'Zero-Lash' length) and pre-load the lifter if required.
Turning the engine through @ one revolution will mark the top of the valve stem to show contact pattern.
The mark being to 'high' (towards the intake manifold) on stem usually indicates the need for more length - the mark being 'low' (towards the exhaust manifold) on the stem indicates you length is to long for your set-up.
Adjust the checker and recheck until the pattern is closely centered in stem and the contact area mark is the smallest/narrowest (width) you can achieve.
This method incorporates all the variables in stack heights in the system and gives you a very accurate length reading.
Do intakes and exhaust on several valves on both sides until you get a good set of base numbers to order your pushrods from.
I do every valve on some engines
Been doing this for years to compensate for block-head stack, lifter type/size, rocker ratio, and valve length ...