The listing is correct. At one point in time there was an episode 5 but it got pulled.

On the Dropout Discord server there is a message from Sam Reich on January 31st, 2020:

"hi again folks, a small group of us just connected (the benefit of being a small team is that we can all assemble easily) and decided that our best course of action, at least for the time being, is to pull the episode. it doesn't represent us or what we stand for well enough to leave up. at a later date, and with the proper resources, we'll consider re-editing the episode, perhaps with a disclaimer.

i hope it goes without saying that we aren't trying to pretend it never existed; rather, we're trying to respond to what we think is some important feedback."

Skimming the discussion, it looks like the episode contained a bad taste joke about Asperger's