The material "Eyebrows" picks up the actual eyebrow area painted on the face. "Upper Eyebrows" reads from the funky area to the upper right of the texture map, just above the spot for the eyelashes. I usually don't even use the "Eyebrows", just not painting them in on the face(or if using someone else's texture, painting away the eyebrows on the map)and go for a transmap on the Upper Brow.