Its strange.
After I saw your post I checked my gift card balance and I see its by me the same.
I bought something earlier in the day, it was 124.99 I selected visa checkout, I entered my staples gift card (bought at 15% discount on ebay), however after submitting the order, it said something like the coupon can't be applied, and it charged 133.74 (tax) I also got an email saying I was charged 133.
I checked now the balance of my gift card and I have left 93, which means I got the $25 off.