For additional reference i added a single refined rock to each plot:
Now this list tells me that refined rock has a base prestige of 6:
It’s hard to guess what’s exactly happening here without the formula. It’s not as simple as +/- 1 for a natural block.
Maybe random but FYI I was able to add some couple thousand prestige to my main build again with 16 empty plots. Again, based on forum derived info and implications I’m into the “built space” modifier for a penalty on too many blocks in my main build anyways.
That may in fact be why the blocks placed above show different values. That in air plot is nearly 100% ‘built’.