Yes, you got it right.
The licensing model is actually pretty straightforward with the “one license = one end product” rule. But the reality of specific cases created exceptions for series, or variations.
If it’s what constitute a series that you find strange or unclear, here’s what Envato is saying about it:
What constitutes a series (eg TV series, webisodes, or a magazine with monthly editions)?
To be considered a series, all things in the series (eg episode, edition) must be connected, and be released within 1 year of the first installment. There is also a maximum of 52 episodes or editions within the series.
Example: A 12 episode TV series that starts in December and ends in July would only require a single license. A YouTube series that releases an episode every week (52 total) would only need to purchase a license once every year. A magazine that releases an edition every other month would need to purchase a license once every year.
As you can see, the definition of a series is a bit loose, and thus at the advantage of the buyer.
Anyway, good luck with your videos and happy creating