Factory heads? With some good lighting, you should be able to look down and get an idea how close the lifter plunger is to the retainer. Is it a spring retainer, or Truarc?
Just looks like a 5/16” pushrod to me.
Compared to my test piece rocker, it appears like that would be a bit less than one turn out.
Sounds like your OK. With the other rockers I have used that have the cup type adjuster, I think the cup gets oil from about the all the way up position to about 3 turns down. If you have zero preload with the adjuster all the way up, and around 0.030"- 0.060" lifter preload with about 1 to 1-1/2 turns down then everything should be good.