this battery can deliver 0.03mA of power

0.03mA of current. That times the 3 volts = 0.1 mW of power.

This is pretty normal, in my opinion. Every time people complain about common core arithmetic there are dozens of us who come out of the woodwork to argue that the concepts being taught are important for deeper understanding of math, beyond just rote memorization of pencil and paper algorithms.