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The same thing happens with Words of Power, I count 38 total, but "Words of Power Unlocked" is only 37, and "Words of Power Unlocked" is 41. Where are the extras coming from?
This doesn't seem to be particularly uncommon either, searching Google for "Shouts Unlocked" "Shouts Learned" shows quite a few people with one more unlocked than learned.
Is this related to learning some of the Words at High Hrothgar instead of through dungeon exploring, or something similar?