Grammar

There is not enough context to really give a good answer, so if you expect help with questions like this, you need to provide complete sentences, and preferably, the sentence before the one in which your phrase appears, and the sentence after that.

I will give it shot--if one assumes that it means kill in the sense of game animals, it would mean the total amount of game killed in three days.

If by what you mean is a query about the phrase 3 Days to Kill,
it's a recent 2014 movie with Kevin Costner. The link to that movie can be found here:
http://www.imdb.com/title/tt2172934/

Ragman, thank you for your reply. After i have seen this film, i still hesitated this idiom. Could you please explain to me detailed meaning and grammar?

You're welcome.

However, I've no idea, frankly. I've never seen the movie. I'd suggest looking at the link I provided and in the plot description at the link for an explanation.
I'd only be guessing if I said that with his assignment he had 3 days deadline to kill someone if I were to take the phrase at its literal meaning.

I've been looking over it a second time and rethinking this a bit more...In conversational every-day English, the expression 'time to kill' means that someone has time to waste...or time on his/her hands. So this phrase would be a play on words.

@Ragman. Thank you for your explanation. "Time to kill" is a better for me on this idiom. ：-）