They heated the plasma with a power of 2.7 MW for 480 s which in total deposited 2.7 MW × 480 s = 1296 MJ, i.e. 1.3 GJ, of energy into the plasma heating it up. That is the energy of 310 kg of TNT (4.184 MJ/kg) or burning 38 l of gasoline (34.2 MJ/l). Keep in mind that this energy was deposited into the plasma which has a mass of only about 10 mg.