I am confused! Are the seving sizes on Earlene's Cakes website for one or two layer cakes? And...just to make sure that I understand, a two layer cake is actually TWO cakes stacked with filling in between. Right? Not one cake cut in half with filling. Right?

You are right on all counts
Yes, her servings are based on a cake 4" tall. (Two 2" layers stacked w/filling b etween)

Thanks, kakeladi! What if I just did one layer torted with filling. Would I just cut the amount of servings in half? That may be a stupid question with an obvious answer, but for some reason, I can not wrap my brain around this!
I am making a cake next week that nees to serve 30. They want a tiered cake, each a different flavor, and I am trying to get it as close to 30 as possible. I was thinking about doing a 1 layer 10"/8"/6" rounds, but was wondering if anyone out there knows how many that would feed.