To add a footnote (using the current footnote font) at the bottom of the chart area, use:

chSet 'Footer' 'My chart'

Typically, this would be used to note the file name used for the chart data, the date and time of preparation, and so on. By default, it is drawn in the lower left corner of the chart area, but you can also choose centred or right alignment by setting the footnote style.

Use semi-colons to split footnotes over multiple lines. To get a semi-colon into a footnote, preceed it with a backslash character.