The tag cloud in the OPAC has a mouseover that shows a number. People expect this to be the number of records that will be shown if you click on it, but it's not. It's actually a weighting of the values, which is mostly meaningless to the end user. I plan to make a syspref that will allow this to be turned off.
Oh, I'm an idiot, I'd already reported this in bug 7642. *** This bug has been marked as a duplicate of bug 7642 ***