It is not fast to know how many votes are missing for a tag synonym to be approved.
I read that they need 4 votes, but inside the tag information.
Users with more than 2500 reputation and a total answer score of 5 or more on the tag, can suggest tag synonyms. Users with a total answer score (total upvotes minus total downvotes) of 5 or more on the tag, can vote for tag synonyms. Suggestions will be automatically approved when they reach a score of 4, and automatically deleted when they reach a score of -2.
What about updating the information in http://stackoverflow.com/tags/synonyms?filter=suggested to have it like this?