Where did my chemistry professor get these numbers?

it was given that the equilibrium amount of NH3 was .2 and the initial 0. therefore the change in NH3 is .2. You then use the coefficients to find the other values. Since there are 2 moles of NH3 per 1 mole N2, the change in N2 is 1/2*(0.2)=0.1 mol. Similarly NH3 to H2 is 2 to 3, so change in H2 is 3/2(0.2)=0.3 mol