From http://forums.musicbrainz.org/viewtopic.php?id=2706

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I've made some edits, the results of which look odd. Starting at http://musicbrainz.org/edit/14467586. I attempted to add a release http://musicbrainz.org/release/24fe1816 ... 083b72e33d to a release group that contained just one release. The existing release had 15 tracks. The Australian release that I was adding only has 14 tracks. [edit: snip] In the editing I used the fifteen track release as the base and just deleted track fifteen. When the new release came up it still had track 15 in it. I thought I had goofed navigating tabs. Checking the "add medium" edit http://musicbrainz.org/edit/14467588 it had the correct 14 tracks, but the release shows 15 tracks.
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This looks quite borked. The edit system shows a different tracklist to what ended up in the DB. Despite the removed track, it looks like it's added the release to re-use the same tracklist as original.