In the scene where Rigg is trying to save the girl who's hair is caught in the gears, she tells him that there is a lock, and the numbers are in the gears. He find the first number, it is a six. He finds the second number, a four, and then the third, a seven. When he is entering the code, however, he is saying "617, 617" over and over again. He enters 617 into the lock, and it works. The number is clearly a four.