I think he is being realistic and i think he did a good job, you wouldn't write this if you asked him or if you knew things like worst-case, average-case, and best-case performance.
If you generate N data (N being choosen randomly in a uniform distribution between 100 and 200), and your data size is S (taken randomly between 50 and 500)..
The best, average and worst case scenario are easy enough to compute, aren't they ? Of course there was more than two variables (maybe 5), but it was not that hard.