@r-w,

You can use viewportMinimum and viewportMaximum properties of axisY and set it to 0 and 99 respectively so that any value above 99 or below 0 are not visualized. Kindly take a look at this code-snippet for an example on your requirement,

axisY: {
  viewportMinimum: 0,
  viewportMaximum: 99
}

You can take a look at this JSFiddle for an example with complete code on the same.

If the solution suggested doesn’t fulfill your requirement, kindly brief us further about your use case with a pictorial representation or an example so that we can understand your scenario better and help you out with an appropriate solution.

—
Adithya Menon
Team CanvasJS