Number one is it transfers a three carbon component, not the two carbon component. So it transfers the dihydroxy acetone. So this structure here has one, two, three carbons and two hydroxyl groups one and two. And so that's why we call this structure a dihydroxy acetone, and it ultimately came from the first product molecule. And this dihydroxy acetone is transferred onto the second product, the second substrate molecule. So this is substrate number one and substrate number two.