Maybe it's a bug in how the game gathers maximum buy offers?
No, it's an artifact of me now calculating the avg number from a different data set than the max/min numbers were based on. It will sort itself out, new data written into the database will not have this problem, but old data does. I could fix it with a few lines of code, but I don't want to, because it fixes itself if you just wait a while.
Oh, and also: I am thinking about removing those numbers. They don't really make all that much sense. I had something else in mind with that, but I can't (currently) do that with the charts library I use.