Definition (時間)
Used to indicate the moment when an action or event will begin or occur simultaneously, after counting to a specified number.
數到三（四，五等）的时候
On the count of three, I expect everyone to stand up.
數到三時，我希望每個人都站起來。
On the count of three, they tossed their grenades into the trench and fled.
數到三時，他們把手榴彈扔進戰壕並逃離。
We’ll start at the same time. On the count of three – one, two, three, go!
我們會同時開始。數到三——一、二、三，開始！