A stem and leaf display shows the values in a data set by groupings. In this case the groupings are each ranges of 10.
1/ includes the values that are 2-digit numbers where the first digit is 1, so that would be numbers from 10 through 19. The values after the slash are the second digit of the number.
So 1/13 means that there are 2 numbers in the group, 11 and 13.
Following this for all three groups, you see that the original values are: