So this equation is telling us that the total amount of enzyme inside our cell, inside that environment is equal to the sum of the free enzyme that is not bound to any substrate plus the enzyme that is bound to that substrate. Now, we know that when the concentration of the substrate is very low, when we're right here, the rate of the enzyme will be low because not much of the substrate will actually be bound to the enzyme. And so that means our E total is equal to approximately the concentration of the free enzyme. Because by making this assumption here, we're saying that inside our cells we have a very low concentration of S. And because we have a low amount of S substrate, not too much substrate will be bound to the enzyme. And so the majority of the enzyme will exist in its free state, not bound to the substrate. And that means the total enzyme is equal to approximately the free enzyme.