In other words, what do you call this (but as a whole):
I made a list of __. Please stop in each of them to describe the scene playing on the screen.
Timestamp would work in this instance. A modern definition of timestamp is:
A digital record of the time of occurrence of a particular event.
It would work in the sentence you provided as well:
I made a list of timestamps. Please stop at each of them to describe the scene playing on the screen.
Note that with timestamp, you'd say you stopped at the timestamp rather than stopped in the timestamp.