The chart can automatically adjust the number of major ticks to a best feasible value. However, if you do not want the chart to do the same, you can add:
<chart ... adjustTM='0' majorTMNumber='8' minorTMNumber='3' ...>
You can opt to show every nth tick value by setting:
<chart ... tickValueStep='2' ...>
This will result in every 2nd major tick mark's value being shown, as under: |