This is the position x,y in percent
This is the dimensions w, h (I think it’s w,h and not h,w)
This is the x,y placement of the center of the source image.
Make yourself a grid background and it makes finding your exact placements much easier. Once I get back to my dev computer I’ll post my theme building theme. I’m not good enough to just know mathematically how things layout so I have to make myself a cheat sheet.