The median of a set of numbers is the middle number in the set (after the numbers have been arranged from least to greatest) -- or, if there are an even number of data, the median is the average of the middle two numbers.

In descending order, the set of numbers is:

13, 15, 16, 19, 19, 22, 25, 25, 26, 27, 28, 29

Median = (22 + 25) / 2 = 23.5