C is the width of the backrest, from one back corner to the other. D is the seat height, measure from floor to top of seat. E is the width of the seat. If the front is wider than the back write in both measurements. F is the depth of the seat.
G is the width of the back, at widest area.
If you have a parson with a shaped back, usually a scroll at the top you need to trace the shape of the scroll. When measuring the total height, place your tape measure against the piece all the way up following the curve, do not by pass the length of the curve shape. If you have a parson with arms you will need to measure the height, length and thickness of the arms.