I recently fixed leaks in my tub spouts by replacing the springs and washers.

The thing I would like explained is this:
I first turned off the water in my house and replaced the parts in the faucet handles.
While the water was still off the faucets were still leaking and one of them was leaking quite a bit more than the original leak. How is this possible? Where is that water coming from?
I got frustrated trying to figure out why it was leaking and out of desperation I turned the water back on. Then I turned the faucets on and off. The leak stopped and has not returned.

I would just like to know how the faucet can leak even while the water is turned off?
Make sense?

It could have been residual water left in the pipes, perhaps the water in the pipe that goes from the tub spout up to the showerhead.