Hello, everyone! In a movie I am translating, two guys are watching a football game on TV. The reporter says: "...he’s got a first down for California. At the thirty-one." I am no sports expert myself and since American football is just a niche sport in our country, there are not many American football experts here, either. I was able to google what "first down" means but what does the "thirty-one" refer to? Is it 31st minute of the game? Please, help me out.