Trying to get this done fast, please excuse typos.
If anyone got a refund for the Bethesda pack or Borderlands 2 four-pack, you now (probably) have a 20% attached to your account that will work for the entire year.
There's an info post on their website that says you can't buy blue coins (an internal loyalty currency you can also buy directly) at 20% off. But you can.
And you can then turn around and use those coins immediately to buy a game at 20% off.
You probably have less than a day before they fix this. Make sure you see something like this before you purchase:
The image shows -200 BLC… so while you get a 20% discount, are you getting 20% less BLC?