So in this case, if we add two of these blue molecules, then that means two of these enzymes will form the enzyme substrate complex, as shown in this diagram. And so this means that exactly half of the active sites will be filled. And another way of saying this is in the following manner. So when the concentration of substrate is equal to Km, the concentration of the enzyme substrate complex. So Es is equal to exactly half of the total initial concentration of that enzyme. So what that means is initially we begin with four enzyme molecules.