I suspect you're thinking of 3.5g amount - which is a typical amount of magic mushrooms to consume. The study is using psilocybin directly. Wikipedia states "T

I suspect you're thinking of 3.5g amount - which is a typical amount of magic mushrooms to consume. The study is using psilocybin directly. Wikipedia states "The concentrations of psilocin and psilocybin ... [is] 0.37–1.30% (dry weight) in the whole mushroom". Assuming about 0.5% concentration, 3.5g of dry mushrooms is about 18mg of psilocybin/psilocin.