Gui : Game Scales

Hey guys! Got a quick question! Working with TGB here. I noticed the X,Y grid is different for GUIs than it is for the 2d scene ie(a gui with the same x,y position as a 2D scene object will show up at a different spot on screen than its counterpart). Is there a scale/ratio or something I can go by so I can calculate exactly where I want that gui to pop up? I'm cranking out some random numbers that will need to pop up above objects' heads.