The FontDPSAFM keyword identifies the directory in which font metrics are stored. Font metrics provide information about each font that improves kerning. At initialisation, the application creates links in the directory /usr/discreet/font that point to font metric files in the directory identified by this keyword.
If you do not specify a directory pathname, the application uses /usr/lib/DPS/AFM. In most cases this directory—created when you installed the Display PostScript software as part of the installation—should be the one identified by the FontDPSAFM keyword.