take 16 hours to charge first time. They are supposed to stay charged up to 22 hours. How is this possible for them to stay charged longer than it charges?

The time they stay charged is deoendent on the amount of power you use, or really, the amount of current. Power is just current times voltage, and the voltage is pretty much constant.

Current is just the number of electrons per second. If you charge at a 10 electrons per second but use only 1 electrons per second, than the device will last 10 times longer than it takes to charge.

Those numbers aren't meant to be realiatic. Real currents are closer to 10,000,000,000,000,000,000 electrons per second.

I would add that most batteries can't be charged too quickly without overheating, so the better chargers tend to limit charging current in the first place, while monitoring battery temperature and further reducing (or cycling off) the charging current when it gets too hot.