Thanks for the details folks. Gives me something to go on with. The guy who adjusted the chain used a laser which he seated against the rear sprocket. So in reality the adjustment hinges on the accuracy of the rear sprocket. As I mentioned in the original post, this meant the tick marks were out by two, and just looked odd.
On a positive note, on the ride home the bike turned left pretty quick. I'll give it some attension this weekend and see if I can get it straight.