It sounds like he was saying that the cycle must happen twice if you start with 1 glucose molecule.
Glycolysis takes 1 molecule of glucose (C6
) and makes 2 molecules of pyruvate. Each pyruvate is then converted to acetyl-CoA through the PDH complex (pyruvate dehydrogenase complex) before it enters the Calvin Cycle. If you started with 1 molecule of glucose, then 2 molecules of acetyl-CoA can enter the Calvin Cycle.