i think its a number that you can set and if someone bids that number you end the auction earlier. for example if you set the GIN at 2300 and someone bids that much then they win and you end the auction but im not sure.
GIN = Get it Now. Before any bidding has happened, you can set a point total (2000 and up) where people can just pay that much in points instead of bidding. Its a feature that is available after you earn your "Seller Wings" badge.