If you don't set min/max on the dependent axes, this fills them in
automatically by calculating min/max dynamically from the data.
You can set just min or just max and this formatter will fill in the other
value for you automatically. For example, if you only set min then this will
set max automatically, but leave min untouched.
Charts can have multiple dependent axes (chart.left & chart.right, for
example.) If you set min/max on some axes but not others, then this formatter
copies your min/max to the un-set axes. For example, if you set up min/max on
only the right axis then your values will be automatically copied to the left
axis. (if you use different min/max values for different axes, the
precendence is undefined. So don't do that.)