Video rendering time is measured in man-hours. How is that calculated?
I've never heard that term used for rendering before, but it is most likely referring to the number of hours of computation needed for a single CPU or GPU to process it.  In most video and 3d applications, it is possible to parallelize the rendering of the video itself (though not necessarily the encoding.

Thus, a job that would take 200 "man hours" (more often called CPU hours when I've heard it used) would only take 20 hours if you had 10 CPUs working on it.