Imagine that you are looking through a microscope. Try to count how many time intervals pass before each cell divides. If you invoke the stopwatch, it will print the age of a cell at division time. There is a flash of red at the cells that were just formed.
We can sympathize with the persons who performed these experiments.
They had to examine hundreds of divisions in order to collect sufficient
data for good graphs. It is not easy to keep track of organisms on a computer
screen. Imagine tracking them in a film of nutrient on a microscope slide
where they move and go out of focus.