Footsites use a cart hold system to try and make a release fair. When you add a product to cart during release time, theoretically the product will be held in your card for around 10 minutes to give you time to checkout. With this, the product may show as out of stock very fast. Most of the time, this does not mean that it is actually out of stock! During footsite drops, people who were not successful in checking out will have their cart lost. This typically happens in waves of about 5 to 10 minutes. When these waves occur, you will see a heavy influx in checkouts.