I have noticed several of the numbers to the left of tags in my profile are inconsistent with the number that it shows when I hover my mouse:
For example, this tag has a 0 beside it but the tool-tip says 8:
They are not. Your tag score is only from answers, so if you have no upvoted answers in the tag, your score will always be 0 (all of this being non-community-wiki of course). The stats for questions is provided in the tooltip just as a so-you-know.