I think we are talking past each other here.
Yes, 1.8 x 10^11 joules is equal to 43 tons of TNT is equal to 1 miligram of antimatter + 1 miligram of matter
Therefore, 1.8 x 10^17 joules, which is 1 million times as much, is equal to 43 mega-tons of TNT and reqires 1 million times as much antimatter, i.e. 1 kg