Version numberig of XEmacs

Greetings, opening XEmacs under Cygwin and clicking on "Help" -> "About XEmacs ..." presents a buffer showing (among other things) the text [version 21.4.24; April 2015] and doing the same under Ubuntu returns a similar [version 21.4.22; April 2015] However when I check the Mercurial log of the repository found at https://bitbucket.org/xemacs/xemacs or look into file "ChangeLog" in aforementioned repository I cannot find such an XEmacs version. According to this file version 21.5.0 "alfalfa" was already released 2001-04-18, the version before this was 21.2.46 "Urania", dating back to 2001-03-21, and the version current in April 2015 aparently was 21.5.34 "kale", released at 2013-06-23. What does version 21.4.* really refer to? Sincerely, Rainer