From Unimatic:

A MODIFICATION WAS PLACED INTO UNIMATIC, WHICH PERMITS BETTER
TRACKING OF HOW TRIPS WERE PICKED UP THROUGH THE TRADE AWARD
PROCESS. TRIPS PICKED UP THROUGH THIS PROCESS WILL NOW HAVE
DIFFERENT LOF ACTION CODES AND WILL SHOW DIFFERENTLY ON LOFITM,
LOFTXN, AND CATS. HERE'S A DESCRIPTION OF EACH OF TRADE TYPE:

TRDO - TRADE WITH OPEN FLYING
TRDF - TRIP TRADE WITH OTHER FLIGHT ATTENDANT
TRDR - RDO TRADE WITH OTHER FLIGHT ATTENDANT
TRDC - CHARTER TRADE
TRDL - LEGALITY TRADE

This info will be updated in the Complete Unimatic as soon as I get the friggin time!