The standard three are an announcement, a release-day post and a follow-up — but they're yours to allocate. Some people want two release-day variants and a show flyer. Some want a story graphic instead of a feed post.
What matters is that they're designed together. Three graphics from one design pass share a visual language; three ordered separately over a month usually don't.
If we designed your cover art, these will pull from it automatically. If not, send us what you have and we'll match it.