Hey girls, I didn't mean to scare you. 15lbs is the MAX and is not required. It is the cutoff point at which I would say: "Okay, Shonie, enough already...let's take it down a notch and stop eating everything in sight". The point about it being "merely weight" is somewhat correct. I can still fit into my clothes (so you KNOW it can't be 10lbs of fat)...but they are somewhat tighter. The "tighter" is typically in the areas of the upper body though...since a lot of women's tops are not cut for a muscular upper body. My pants are actually looser after some time -- although they do get tight when I first start a bulking cycle.
I'm not sure if others here experience this -- but, with legs, mine get bigger before they get smaller (if that makes any sense). So I don't freak out if my pants are getting a bit snug when I begin a bulking phase. Limiting carbs (but keeping calories the same) helps.
Like Pinky said, she gains much less than that! But you must be willing to gain something...otherwise you'll have a hard time gaining muscle.
Shonie