You can additional commentary to your graph with XYOutS
After the XYOuts command you must add two numbers. The first is the position along the X axis where the text string will be printed. The second number indicates the location along the Y axis. NOTE: This line must be added after the Plot command has been issued.
XYOutS, 3, 9.2, 'Text goes here'
For a complex example combining the use of XYOutS and POSITION, visit How-To site, Make Axis Titles Larger Than Axis Values