Can't properly scale down mouse coordinates to a smaller RenderTarget

Input
6

Hello. I tried doing what you said, and using your normalize methods, and I got this

            Single xpos1 = Extra.Normalize(ms.X - r.X, 
                (Single)Globals.WindowSize.Width, 
                (Single)Globals.WindowSize.Height
            );
            Single ypos1 = Extra.Normalize(ms.Y - r.Y, 
                (Single)Globals.WindowSize.Width, 
                (Single)Globals.WindowSize.Height
            );
            Single xpos2 = Extra.Denormalize(xpos1, 
                (Single)Globals.RenderSize.Width, 
                (Single)Globals.RenderSize.Height
            );
            Single ypos2 = Extra.Denormalize(ypos1, 
                (Single)Globals.RenderSize.Width, 
                (Single)Globals.RenderSize.Height
            );
            pos = new Vector2(
                (xpos2 + (Globals.Camera.Position.X - (Single)(Globals.RenderSize.Width / 2))),
                (ypos2 + (Globals.Camera.Position.Y - (Single)(Globals.RenderSize.Height / 2)))
            );

It doesn’t seem to work, though. It also still has the issue of the real mouse moving further from the in-game mouse as it moves towards the bottom right.
I’m not sure what you mean by make the Y value Height?
I don’t think I’m properly interpreting your instructions. Is there any way you could write some pseudo-code for it?