Hi SouthATL_992,
As you mention you want to put MAY underneath in the center, we would like to suggestion you as a workaround you try my step below, hope it meet your goal.
To add a second horizontal axis, you first need to add a second vertical axis(only then will the options of second horizontal axis get activated).
After Choose Secondary Axis now, click anywhere is graph. This will enable Design tab. Under Design tab > Add Chart Elements > Axes Title> second horizontal and test box will appear in center of chart then write the name MAY.
Let us know if you need further assistance.
Best Regards,
Waqas Muhammad