In Drip feeds, each episode is released a number of days after the previous episode.
The first episode must be available immediately (0 drip days) because apps require at least 1 episode available at the time of subscribing.
If a later episode is 0 days, then the episode is released at the same time as the previous one.
Listeners will only see what's been released based on their start date.
Not all listeners see the same episodes.
The Universal Link shouldn't be used for Drip feeds. That link's start date is the day you created the feed, and everyone using that link will see content as though they were added to the feed on that day.
Know that Spotify pulls content from the Universal Link, so Spotify won't show the proper Drip schedule of your feed for listeners. It's recommend to not use Spotify for Drip feeds.
Drip feeds are useful for membership sites, or an evergreen challenge where material is released over a length time.