So we have the red enzymes and we have the active side. So the total concentration is three. Now, once we add, let's say, three blue substrate molecules into the mixture, those molecules will bind onto the active side. And once all the active sides are completely filled. This is when the enzyme mixture is operating at a maximum velocity, at a maximum rate. And in this moment in time, the concentration of the enzyme substrate complex, which is this here, is equal to the initial total concentration of that enzyme.