Unlike the chicken chop where the meat is lean, lamb brings its own fat to the party. There is marbling running through the chops and a strip of fat along the bone, so even grilled, the meat itself is a chunky 350 plus calories before you touch the sides.
Then you add fries and a ladle of black pepper sauce, which is usually butter and flour based, and you are at 680. It is a good protein meal at 40g, but it is not a light one. If you want it leaner, trim the fat strip off the chops and put the sauce on the side.