http://img208.imageshack.us/img208/5133/wthm.jpg
If it helps, i know it's on the first octant (everything is positive)

x=[0,1]

y=[0,1]

z>0

It seems like a sphere of radius 2 on the first octant, but then they put

which is the projection of a circle on the first quadrant (because x belongs to [0,1]) of radius 1.

So i'ts kind of weird. If it is what i think, they might as well have put a cylinder z=[0,1] and then the rest of the sphere of radius 2 above it, being all values positive (first octant).