The number of breaths depends on the individual and the depth. I carried a HEEDS bottle (spare air) in the military and they are generally designed to supply roughly 30 breaths. There is a difference between sitting at the surface and taking 30 breaths over being in panic mode being pulled down in a helo so the reported number of breaths will most likely be greatly reduced and dependent on the individual. While a spare air is better than nothing, it would be my last choice as a bail out option for diving.