Okay, I still don't get why it doesn't give it the correct scale. The only parent to this gameobject is a UIPanel with scales all 1.
Style is set to both, X = 1 and Y = 1. ScaleX = 586.6667 & ScaleY = 440.
Camera is orthographic with size: 540, clipping planes : (-500 , 500)
I have two issues here:
1) I think it should be getting the real width and real hight (not screen width and screen hight) by using screenToWorld coords.
2) It's getting the wrong scales. - Height should be 2 x ortho size.