Words, time and what you can infer
Counting words seems trivial, but it's one of the most useful measures for content creators: you can estimate how long a text takes to read, how much narration it yields and whether a block is too long for one screen.
We use ~220 words per minute for silent reading and ~140 for narration — comfortable, conservative rates. The number of sentences and paragraphs helps gauge density: very long paragraphs usually need breaking up.
Need a full course estimate, with pauses and interactions? Use the Course duration calculator.