Both means are less than 15, then adding a score of 15 would increase the mean for either team.
The median of team B is 15, then adding a score of 15 would not increase the median for team B
Adding a score of 15 to Team A would increase team A's mean, and in consequence, it would decrease the difference between the mean scores.
Adding a score of 15 to Team B would increase team B's mean, and in consequence, it would increase the difference between the mean scores.
Adding a score of 15 to Team A would increase team A's median, and in consequence, it would decrease the difference between the median scores.