Usually W = Width, D = Depth & H = Height.
Therefore A = 500, B = 500 & D = 430.
Note:
Sometimes D = Depth of seat only, which would be "C" in your drawing.
But I would read that as D = Depth overall, which is "B" in your drawing.
Anyway I am sure Mr T will be along with the correct answer shortly.
Cheers, Paul.
