@Pokemon #025 Even if I don't get into all the technical details about probability, I can tell you that 2-4 items can spawn together. The chance of finding 2 old ambers among 4 items is obviously higher than finding them among 2 items. You don't seem to be considering that, among a bunch of other things you didn't consider.
@Dialga If you don't like the answer then don't select it.