Comments of chapter undefined of I Am Loaded with Passive Skills

Since when is 12+18+22=40? Did the author skip his math classes or is it just the translator being bad as usual? The first doubled and sold for 12 billion, the second tripled and sold for 18 billion and the third almost quadrupled, selling for 22 billion. 12+18 = 30, 30+22 = 52. Not really rocket science.