postfix monitoring plugin from xymonton -- graphs not working

I am using this plugin:

https://wiki.xymonton.org/doku.php/monitors:postfix

It works well, except the graphing.  I made the suggested edits to the
xymon config.  I assume that either I screwed something up or the docs
are out of date.

What can I do to get the graphs working?  If info is needed to pinpoint
the problem, please let me know and I will send it.

Thanks,
Shawn