It sounds like stored value to me...

Oh and also there should be another restriction: You can only use it on a ticket that costs MORE than the actual value of the credit.

I had this issue with a credit my girlfriend has as well. A huge PITA, her credit was 1400$ and we booked a flight to Paris for 1100$ after a huge argument. I escalated it to WHQ and got the remaining 300$ via voucher from CR. But that was 3 years ago...

I read that clause recently again in some relation.

So be careful!