Just curious what exactly the 10/20 marks on the sub-dials mean on some of my clocks. Is this minutes gained per hour, per day, per week? Or is it just some decoration? Never sure of the purpose of these sub-dials besides some convenience, since it seems like fine tuning takes place by adjusting the bob directly. Any ideas? Attached is 2 of my clocks - a Peerless and a Winterhalder.