I would like to order the channel balance for my non-tilt window. The width of the leaf is approx 51 inches and the height is about 32 inches. I believe my window's brand is Kinco. The current balance has the following numbers stamped: 29 9 GW CMC 11. Am I supposed to order a 28 or 29 lbs? Are those numbers good to determine the right sash weight? What part number should I order? Please let me know. Thanks.