New Tag Logic?

How does the tag logic work?  It is understandable how the categories work as each is assigned a location and a number to associate itself with the page.  But how does the logic work for tags now?  Before it was just added it and it pulls them all. Now I am not so sure...But it probably is because my tags were to long.  But I wish I had a better handle on the new logic so I can fix the newly added.

1.   Does it only take one tag to be entered to look for all others if clicked on?
2.   Does it now take ALL tags to be put in the tag table to be reached?

Any help would be greatly appreciated to understand the newer logic.  I am sure I am not the only one that needs to understand this.

****This is because of a import to the database and not a manual entry...

Has anyone tested this at all or looked at it?  As I hover over a tag it say 56 but returns fewer and vice versa?  It would be very helpful to know what makes this work as before it would always pull whatever was there now it says 56 and pulls none 56 is correct but obviously 0 is not... 

Really that's interesting indeed...