The two light gray dashed lines split the chart into 4 regions or quadrants.
The horizontal gray dashed line at 0.5 on the importance scale on the Y-axis, is the threshold usually accepted at which point a driver becomes a reliable and accurate predictor of the outcome metric.
The vertical gray dashed line on the performance scale on the X-axis, is the threshold of when average scores change from performing well to performing poorly. The default is usual the average score of all the potential drivers.
The key driver chart has four quadrants: