I already told you. He used 1 half APM tank = 1 tank. He probably also used standard sized tanks. And for some reason only 3 big tanks in the center building
So now you have 72 tanks on the left 72 tanks on the right and 3x12 = 36 in the center.
Come on guys, you can count in an eternity. The example in the presentation is just an illustration of how the grow out staging works like and how effective it is.