I think you may have looked at table A2.3 for crew positions. Table A2.2 reads as follows:
Authorized Mission Symbols (Note: Only mission symbols listed in this table are valid. In ARMS the mission symbol is a five-character field. The first two characters must be IAW this table. MAJCOMs may assign additional characters as required (see Notes 1 and 2 at end of table).
CA, CC, Air Rescue CF Coded Aircraft Missions, and TF Coded Aircraft Missions as applicable
A1 Scheduled Flights. Missions where the main goal is to move cargo or passengers on a scheduled frequency.
A4 Nonscheduled Logistics. Missions where the main goal is to move cargo or passengers on other than scheduled flights.
A5 Positioning or Repositioning. The nonproductive part of a flight that is required to locate an aircraft at a station for onloading or returning an aircraft to home station.
T2 Formal Major Weapon System (MWS) Training. Instruction and training of pilots and crews undergoing initial MWS crew training in designated Formal Training Units.
O3 Aircraft Delivery. Aircraft delivery flights under the control of Air Combat Command (ACC), including inter-command transfers; US Air Force, Navy, or other pilots attached to ACC for purposes of delivering aircraft delivery organizations as well as "borrowed" crews. Also includes aircraft deliveries other than under ACC control.
There is an expanded 4 digit mission symbol code listing in G081 for AMC aircraft.