Grimm Fandango said:You can't apply the credit to existing preorders period. You'll need to make a new order to use it.
Say you already preordered Halo Reach and want to use this credit for it. The only way to do so is to preorder the game again (and delete your old preorder if you wish). The credit should automatically work during checkout.
^Awesome. Thanks for the explanation.^
I'm almost embarrassed to admit this, but I've logged around 20+ hours and I'm only at 26%.