Can't help you there, as I said before when I test valves I look at a mutual characteristics graph, like this one for the 6SN7 - see attached and find a place where Va, Ia and Vg cross. Here on this sheet it might be Va 225v, Ia 5mA, Vg -8v. So I'd start by setting Vg to -8v, turn on heater PSU, check it's at 6.3v , then bring up Va till it's at 225v, if the Ia meter reads 5mA or near, the valves a good un.
How a valve behaves when testing can tell you a lot, for instance, heater flash, if Va dances about or won't settle, or if Vg moves whilst bringing up Va might indicate a short or similar. After testing a few hundred valves you get to know when a valve is good or suspect. A good valve will slowly climb to the expected Ia, bad ones linger about about looking solemn and shifty whilst muttering under their breath : )
This chap did a few video's on valve testers you might find interesting -
https://www.youtube.com/watch?v=TtVbTSAKx7k
Andy.