So when all the active sites are occupied by the substrate, what that basically means is the enzyme substrate complex concentration, Es, is equal to the initial total concentration of that enzyme. So to see what we mean by that, let's take a look at the following diagram. So let's suppose initially inside Arabica, before we added the substrate, we contained three of these identical enzymes. 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.