Stem: The numbers to the left of the line, and Leaf: The numbers to the right of the line.

We have, 28, 28, 50, 1:00, 1:02, 2:20, 2:25, 2:35, 2:43, 2:45, 3:00, 3:00, 3:00, 3:30, 3:36, 4:00, 4:00.

Finding the middle, we get 2 minutes and 43 seconds, so 120+43=163 seconds.