Axis Scale on Numbers

I recently got a new laptop and am having trouble with axis scaling. I remember on my older Mac I could easily change the axis scale by clicking on the chart> axis> axis scale but now I cannot find anyway of changing the scale at all. I tried using the custom intervals tab of the drop down menu in axis but can't figure that out...maybe that's how this is to be done. Ive resorted to creating text boxes and typing out my scale that way but it looks horrible. I am hoping someone can help me change the scale like I could in the good ole days. All I want is a y-axis in intervals of five rather than the default of six.

Thanks in advance!