Other mistake: When Dr. Strange rushes a patient to brain surgery they show him and Dr. Christine Palmer operating without surgical masks. When they cut away and come back they're wearing masks. Also, Dr. Palmer is an ER doctor, and her assisting him would never happen in real life.
Other mistake: After the fight where his sling ring is stolen by Kaecilius, he has a sling ring in his possession and uses it to jump to Hong Kong.
Answer: I took it to mean Dr. Strange could hear the watch ticking, and he wanted complete silence.