Gerald, I'm not sure how to answer that question--but I'm also not sure that the semantics matter.
If you'd gone on to provide a lesson for your readers, perhaps on Satan's lies, it'd be non-fiction with an opening anecdote.
If you'd gone on to tell a narrative about the actual events in that class, based on actual events, it'd still be non-fiction. I guess we'd just call it a first-person account. These can read very much like fiction--with dialog, characters, conflict, etc. I don't really think it matters if characters are combined, dialog is altered, that sort of thing. No one's memory of any event is absolutely accurate.
If you'd written a narrative simply "based on" or "inspired by" your experiences with that class, it'd be fiction. And the difference between this and the preceding paragraph is shades of gray.
I guess the only place where it would matter would be in a contest where the requirement was to write non-fiction, or something along that line. But in the Writing Challenge, fiction and non-fiction are judged side-by-side--so I really don't think it's an issue.
Every time I've written a story based on my own true life events, I've fiddled with it, either to make it more interesting, or clearer to the reader, or funnier, or sadder, or less recognizable, or something. There's nothing wrong with that, unless there's someone in the story who would be hurt or upset by its alteration, or if the deception somehow harms the reader. It's not lying, it's writing.
Did I come anywhere close to addressing your question?