Edits within 5 minutes of making a post or editing a post are rolled into one revision. (For the bounty grace period of 24 hours, use the [expired-bounty] tag instead.)
(Note: The term "grace period" is also used for the 24-hour term at the end of a bounty in which the main bounty period has expired, but the bounty may still be awarded. For questions about that, do not use this tag; use the tag expired-bounty instead.)
The grace period, or "the ninja edit zone," is a five minute period from the start of an edit to the end timestamp where an author is allowed to make successive changes to a post and have them all displayed under the same revision.
If another author edits inside that five minute period, a rip in the timeline will occur and the grace period will be rendered null and void and the edits will each appear as separate revisions in the post history.
This has always been a feature since the early days of Stack Overflow:
I also try to copy a lot of things I've seen online that have been successful, like conventions. Let me give you a specific example: PHP-BB, and I'm sure there are other web discussion boards that do this too but PHP-BB is the one I know, has this editing convention.
When you post you can edit your own posts, and I noticed that when people are using PHP-BB that right after you post something you'll always notice some goofy mistake that you made, like immediately. This happens to me nine times out of ten I'll post and think "oh, I should have talked about this" or "I missed that word," so you immediately go in and edit. At a certain threshold these are not treated as real edits, they're treated as just going back in time to pretend that it is the post you originally made. It doesn't kick off the whole auditing trail of you having edited it 50 times.
One of the first things we did in Stack Overflow is actually implement that. I remember talking to Geoff Dalgas about that, and he's like "why do we have to have this?" I said, "you don't understand, this feature has to be in there on day 1 otherwise we're going to have so many revisions that are just in the first minute or two after posting and are just silly little things that are being corrected."
You not actually recording the revision? You're not doing the diff thing?
[Not] within the threshold. Right now the threshold is actually 5 minutes. So up to 5 minutes after you post, if you edit your own stuff. Now if I go edit it, it's a real revision.