Most printer manufacturers digitize their fonts at the highest resolution supported by the printer. The VertRes control contains the vertical resolution that the printer manufacture used to digitize a font. This value is specified in dots-per-inch (dpi).
For the Diconix 150 Plus printer, the fonts were digitized at a vertical resolution of 96 dpi. However, in order to prevent possible confusion with calculations between master units in the minidriver data and the units used to express values in the PFM files, the value is 576.