The CR2032 was designed for currents less than 3mA. If you use it at 10X times that, you will not get all of the 240mah.

You assumed that the mah will double when using two batteries in series. That is not true. You will get 6 volts at 240mah. Not 480mah.

Data at
http://www.renata.com/pdf/3vlithium/DBCR2032.05.pdf