I don't understand Case 2.

If meeting the outdoor airflow rates in Case 1 is not feasible because of the physical constraints of the existing ventilation system (...). Supply the maximum possible to reach the minimum setpoint in Case 1 

How can the minimum setpoint in Case 1 be reached if "meeting the outdoor airflow rates in Case 1 is not feasible"? Probably I'm misunderstanding the meaning of "minimum setpoint".

Best Regards