Zero Affinity determines the likelihood that the chart's Y-axis will start at zero, or another number closer to the range of the chart data. For example, if a chart's data range was 1010 to 1200, it makes sense for the Y-axis to start at 1000. Zero Affinity can be between 0 and 1. A value closer to 0 increases the chance that the Y-axis will not start at 0. A value of 1 causes the Y-axis to always start at 0. The default value is .8.