Good question and I’m not sure how our methodoloy works (that’s not my dept) but since I’ll be writing a wrap-up dev blog with some cool statistics from the event and I’ll try to find out what I can and share it so people can understand how we arrived at our conclusions.
I’m certain our numbers will differ from those on zKill and all I can say is keep in mind that third party sources (as awesome as they are) shouldn’t be regarded as official.