i want to travel from beijing to hanoi in veitnam and hoping to use the 72 hour visa

i arrive in beijing at 14:40 on monday and will be leaving beijing at 13:00 on thursday which i know is fine. only snag is the flight lands in hong kong at 16:25 i have to wait 1 hour 20 before leaving hong kong at 17:45 will i be in breach of my 72 hour free transit? I'm from the uk