Issuing shares is a move done to raise money. It would then follow that GameStop would want to get the most money possible for these shares so they would try to sell them for the highest price possible, somewhere around the current going price. I’m not 100% on whether they have to release them all at once but I’m guessing dumping multiple million shares all at once would crash the price which isn’t good for anyone in normal circumstances so it’s probably not done that way. Regardless, there are like 50-60M shares currently shorted — there’s no chance GameStop would issue that many.