In http://forums.musicbrainz.org/viewtopic.php?id=4521 shutterfreak reported the following issue:

Some releases have track sub numbering, e.g.:
http://musicbrainz.org/release/0267eb1f-8259-426f-b7aa-e1906b86b228

When reading this release in Picard, the sub tracks are counted as tracks, so 1.01 becomes 2, and 2 becomes 3 etc... eventually resulting in skewed track numbers.

Is this a bug?