I am not sure why I got 65. It shows up on my receipt as:
Subtotal... 43.75
Bonus... 21.75
Giftcard... 65.00
I assumed the extra 5 was to cover any tax when purchasing a new game but I am not sure.
Just a heads up, I got back from Hastings and traded 3 off their list. Didn't have to ask for any promotion since it applied automatically.
I ended up with 65 in credit put on a giftcard for me after trading in Gears 2, Tiger Woods 09, and Brothers in Arms:HH.
Not bad if you ask me.