The display size is probably misdetected for some reason. You should be able to override it in the Screen section (using the DisplaySize directive) or with the -dpi command line switch.
Thanks. I have in fact discovered how to override using -dpi (and I wasn't aware of DisplaySize, so that is a helpful suggestion, too).
I just thought this was something you or the upstream might want to be aware of. Do what you will with it. :-)
--LG