These are "trusted users" - those with non-zero trust rank that we use to filter spam. You can turn-on raw numbers if you want, but those are meaningless and fluctuate wildly. I don't think anyone else even attempted to calculate some sane numbers that filter out bots, so there's nothing to compare to. We published our raw event data sets a while ago, if anyone wants to run their own numbers, I'd be happy to see an alternative view.