At the time you asked this, the duplicate-questions tag did have only 14 questions in it. The rest still had exact-duplicates.
As Tinkeringbell noted, the master and synonym were swapped a while back - but the tags were never merged, thus leaving the bulk of the questions with the former master.
The question list for the tag presents all questions with either the tag or any of its synonyms, so it will tend to contain more questions than those with the tag, until all synonyms are merged.
This is clearly not an ideal situation, so I've gone ahead and merged the tags. The counts should now be sensible.