Base on the story, the characters changed their feeling when Jackson counted and there were thirteen. They were scared and they tried to think that Jackson was wrong but Jackson was sure that he counted thirteen twice. After that, they still played smee but everyone still though about who was the thirteen. . I think that the thirteen has its own meaning. As we can see, in the western culture, the number 12 is the good number and it means the twelve followers of Jesus Christ and the number 13 is the representative of bad or unlucky.