We are given that the probability of winning a game is 7/1000.
Recall that the probability of an event is given by
As you can see, the probability is the ratio of the number of outcomes we are interested in and the total number of outcomes.
For the given case, the probability 7/1000 means that there are 7 ways to win the game and the total number of ways is 1000.
Or in other words, if you play the game 1000 times, you are most likely to win the game 7 times.