Now, in this particular case, because we had the barrier, energy could not have moved to this side because of that barrier. But as soon as we removed that, the molecules tend to move to the other side. And as the molecules move, they also carry that energy. And mathematically, the most probable case is the case when we have three molecules on this side and three molecules on the other side. This is the state that has the highest entropy because it's the most probable state. And notice in this case we have three units of energy on this side because we have three molecules and we have three units of energy on the other side.