DrawLine GUI confusion

I am using the DrawLine function from http://wiki.unity3d.com/index.php?title=DrawLine I am just doing the following 3 calls and I would think that all three of these lines would start at the same spot. Only the vertical line works the way I would think it should. Can someone explain why the 2nd and 3rd DrawLine are not starting at 450,200?

 void OnGUI() {
 GUI.Box(new Rect(450,200, 100,200), "Box");
 Drawing.DrawLine (new Vector2(450,200), new Vector2(550,200) , Color.white, BorderSize);
 Drawing.DrawLine (new Vector2(450,200), new Vector2(450,400) , Color.green, BorderSize);
 Drawing.DrawLine (new Vector2(450,200), new Vector2(550,400) , Color.yellow, BorderSize);

 }

Here is an image of the issue. The top left corner of the box is (450,200). i would think that all the lines would start there but you see two of them do not.