I was also confused with the direct meaning but if you look at the 1st page of this thread it says:
FORMAT:
Next appointment number)
/SAF forum name: self, DD, DS
/Notified of Appointment Date
/Accepted or Declined or Undecided
/Nom sources
/via MAPS, Foundation prep, self-prep, college re-applicant or applicant, direct appoint from HS, enlisted, re-appointment
/State
My understanding is that direct as a category should only be used for HS senior applicant. If a candidate is enlisted then enlisted should be the category while college applicant should be college applicant?
My 2 cents - A senior HS applicant who eventually get an appointment on his/her first try is a stat worth noting and thus has its own category as the OP reflected.