The real reason that you're seeing torque numbers below what I'm stating is because - the initial operation has already been done. The threads are already stretched, from the real install, the initial operation of building the barrel.
You're taking apart barrels, extensions, and applying torque (hopefully) to realign your extension with the feedramps that were cut in - a later barrel assembly process... You are torquing it again, after the threads were torqued and stretched to spec the first time. Your torque values that you are seeing are torque values from stretched threads... and lower than spec, because of that. That's the reason that you have a torque range, and not a direct number.
Hope that makes sense. Look forward to your intro, in this section here (I'll link it for you):
This is the Intro Section, just click it, and make your post about you:
https://forum.308ar.com/forum/22-introductions/