Yes, Chris from Musical Surroundings was nice to respond to my query and explain it. I did know it couldn't be dB as some of the numbers go higher than the carts channel separation figures!From what I understand, the numbers do not mean anything. They are there for reference only I believe, essentially the VU meter will show a higher number based on the output of the cartridge.
Theoretically the number should rise slightly once you get the azimuth in its most optimal position as the stylus will then be reading and getting the most info from the groove walls.