Significance of V4-V11 on Thor mono blocks

I have a pair of Thor Audio monoblocks which are 150 watts
per channel. I noticed when biasing the amps, each monoblock has next to each tube from v4-v11 next to the bias controls which are on top of the amp. What significance does this have? Do I need to purchase tubes
that specifically fit v4-v11. Are there tubes that go with a v-2 output tube, etc. Where can I read up on this.
You know, I am at a loss, when Paul Marks was around from Thor Audio, he was a phone call away. I remember when I heard a noise on my Thor Tubed Dac. I described it to him and he told me I needed a new 6922 tube for the Dac. I replaced the tube and the problem went away. Now I am a little nervouse how to proceed with tube changing by myself. For instance a memeber said try the JJKT-77 tube
when I need to replace my el-34's. Issues like are the bias settings the same come to mind, from tube to tube the same. Right now I set my bias on each tube to 245 on Thor audios monoblocks. Why, Paul said that after he experimented that produced the best sound and tube wear.. Any guidnace owuld be appreciated. By the way I am listening to Frank Sinatra "Only the Lonely", Cd and have to tell you it is breathtaking. Try it.
absolutely breathtaking. That man could really interpret music.
I believe these are simply tube numbering that reference back to the schematic. You probably also have V1, V2, and V3, right? If you want to try a replacement tube different than you have currently, I would google "your tube substitution", replacing "your tube" with what you currently use. It will give you a number of references that may give you the answer.