When I just tried it to see what it would do it said
HERTZ #1 NUMBER IS NOT ENROLLED IN HERTZ #1 AWARDS [DE628]
so I would assume it's a Hertz #1 discount.
Once I was logged in it took the discount and on a 3 day weekend make believe rental at $60.48 a day and deducted $67 from the total cost. Not too shabby. $174 with the code, $242 without it.