Botox worked immediately! Is it normal that it works this fast?

Hi, this is my third time getting Botox. I know you should start seeing results few days, and the last time when I told my Dr that I see huge difference in a day, he didn't believe me. So this time same thing happened. It's been 10 hours after the procedure and I'm completely frozen. Is that normal that it works that fast?? I'm 25, thick skin, have a little wrinkle between brows, and did 15 units today. (Crow line and little in a forehead)