Printronix ProLine 5 Series Manual page 120

PSeries Dbl High
This menu option allows printing compatibility between the current and older
models of Printronix printers.
Normal: This is normal Double High printing for current model printers.
P3/4/6/9 Compat: Where older printers printed two dot rows higher, this
option allows for compatibility by raising the print two dot rows to match
the current models dot row value (two dot rows lower).
Configuration Menus 4–67