The way most comics use it, One Episode = One Update.
Your subscribers get a comic update notification when you post a new episode. If you add more images to an existing episode, you can tell it to notify your readers, but it will be an activity notification instead, which don't go to mobile users, and sometimes get lost in comment replies and wall posts, and it will say "so and so has edited an episode" instead of calling it an update.
The other problem with using "episodes" as chapters is that the Tapas website pays attention to how many likes and comments and views you get on an episode to determine when a comic is popular or trending -- but people can only like an episode once. So if you add new pages to an episode, nobody can add a new "like" because they've already Liked that episode.
Some people update with a bunch of pages at once, so it's called "an episode" instead of a page so that you can put as many pages in one update as you want. But plenty of folks will just make one episode = one page, if they just update with one page an update (this is what I did).
