I've edited the body of this answer ([link to the answer's revision history](http://askubuntu.com/posts/694747/revisions)) twice after ~21 minutes I initially posted it, the second edit ~3 minutes after the first edit, but the 5 minutes grace period for those two consecutive edits didn't apply; in fact the revision history shows two different revisions, one ~3 minutes after the other (revision 3 ~3 minutes after revision 2).

What happened to the grace period here?

Revision 2: 2015-11-06 **15:02:50**:

[![screenshot1][1]][1]

Revision 3: 2015-11-06 **15:05:06**:

[![screenshot2][2]][2]


  [1]: https://i.sstatic.net/zj4ta.png
  [2]: https://i.sstatic.net/sUCaO.png