@didileking,
With the help of get method, you can get to know the maximum of primary y-axis. Once you get the maximum of primary y-axis, you can use set method to set the maximum of secondary y-axis. Below is the code-snippet to do so.
chart.axisY2[0].set("maximum", chart.axisY[0].get("maximum"));
—
Vishwas R
Team CanvasJS