Carl tells Yon that they can get out of the gate through exit b. They will meet up with Miss Zhuang and Dr. Nadall in the Central Control Room first then exit through exit a. Yon asks Dr. amanda to watch the surveillance monitor for him. He's not sure if there's any zombies in the passage outside of the Security Office, but he's also not sure whether it's safe outside. So he needs to go outside and look for any signs of danger. If he sees anything, he'll signal the Doctor to let him in.