Occasionally gruff will produce a graph with normal y-axis values, except for the segment which cuts very close to the
value 0, for which it produces a string of 9's that run off the side of the graph. I've attached an example of this.
The maximum value of this graph was 0.74 and the minimum value was -1.77. Gruff chose a y-axis which went from -1.77
to 0.71 in 4 steps.