See my edit above for an important additional message.

As far as the extra wire: that's the signal wire that go directly from the outside pin of one digital port of the EZB to the servo signal wire. You run the power wires (+ and -) from your power source (the EZB it's self or and external power supply like a battery) through this unit and to the servo.

How many Amps are in a volt? or is that even correct? (ps, sorry about all the questions)

Two different things. Simplistically, The amps are the power (electrons) that runs the motor and the voltage is the pressure that pushes the electrons through the circuit. Imagine shaking up a bottle of soda and uncorking it. The Amps would be the soda and the pressure pushing it out of the bottle would be the voltage. There's really a little more to it then that but you should get the idea for this description. It's really not a compacted theory and one worth learning about.