DrawMerge, as the name implies, was originally written to create merge files in the rather peculiar merge text format that CorelDRAW requires.
If you intend to use DrawMerge with CorelDRAW print merges, leave this box checked. DrawMerge will output merge files that CorelDRAW will happily eat.
If you plan to DrawMerge's output in some other program that wants plain lists of numbers, remove the checkmark next to Format output for CorelDRAW merge