why you sell 85%? stolen card?
85% is probably about the market price for amazon gift cards. Most gift cards sell at a discount because they can only be used at a specific store, a store that someone may not have a need to buy from.
Gift cards of other stores often sell for a larger discount.
I don't think the fact that the OP is selling for 85% means that the gift card is probably stolen, although the fact that the OP is a newbie means that there is a much higher chance of him selling a carded gift card