What is the recommended maximum length of an RS-530 cable?

RS 530 has a logarithmic degradation on cable length as the data signaling rate increases. These are some of the readings on the chart: up to 90k b/s - 1.2k meters.....400k b/s - 300 meters....1.2 M b/s - 100 meters approx......2 M b/s - 40 meters....6 M b/s - 20 meters...10 M b/s - approx 15 meters....