Sorry, but have to respectfully disagree: Selective multiplayer has a direct effect on the drop rate, as it multiplies the number of available scenes by the number of players spawning new instances of the same scene. More instances = more spawns = drops happening faster than a simple drop percentage on a timed spawn would normally allow. If you intended on only so many possibilities being generated, a model the sieges obviously follow, to control it perfectly the drop rate would have to be dynamically controlled based on the number of spawns happening. To control it less perfectly, you get an average number of spawns over a particular time frame, and divide the intended percentage by average number of spawns. Not a whole lot of deep math there.