Chicken bones are soft, small, and contain hollow areas throughout, so you need about 90 minutes with a pressure cooker to extract enough collagen from the bones to make a rich, gelatinous bone broth. If you have meat in there that you intend on using, then you need to cook the broth in two separate steps. You remove the cooked chicken as soon as it's perfectly cooked, and put the bones and skin back into the Instant Pot to finish breaking down the collagen in the cartilage and bones.