Your guess is as good as mine.
4 seconds sound clip from the The Princess Bride (1987) movie soundboard.
You can hear this line at 01:15:29 in the Blu-ray version of the movie.
Quote context
[...]
- We can't wait. The wedding's in half an hour.
- We must strike in the hustle and the bustle beforehand.
- Tilt his head back. Open his mouth.
- How long do we have to wait before we know if the miracle works?
- Your guess is as good as mine.
- I'll beat you two apart. I'll take you both together!
- You've been mostly dead all day.
- We had Miracle Max make a pill to bring you back.
[...]