A GIN is the acronym for "get it now" which is the fixed amount of credits you want for the item. I think you have the wings that allows you to put one up. This GIN must be placed before the first bid and can be there throughout the auction in case anyone wants it and is willing to give you the amount of credits you want for it. I hope I explaind myself correctly and clearly. The amount is up to you but it does have to be reasonable if you want someone to actually get it now.
I guess if the option was not given to you when you listed the item or when updating it then you don't have it yet. No worries, I plan to bid and I'll continue to watch. : )