CODES:
8888 = NO DRG SYSTEM WAS USED
9999 = UNKNOWN

OTHERWISE, THE FOLLWING CODES ARE USED TO FILL THE FIELD:
IN THE LEFT-MOST 2 POSITIONS:
PP = WHERE "PP" IS US POSTAL CODE FOR THE STATE, IF THE DRG VALUES ARE FROM A SYSTEM DEVELOPED BY
 THE STATE.
HG = IF THE DRG VALUES ARE FROM THE CMS SYSTEM.
XX = IF THE DRG VALUES ARE FROM ANOTHER SYSTEM.

IN THE RIGHT-MOST 2 POSITIONS:
NN = WHERE "NN" IS THE DRG VERSION THAT WAS USED (VALUE 01-98).
99 = VERSION IS UNKNOWN.