How does Improved Uncanny Dodge work on BGTSCC?

[samb123]

I was looking at Assassin (also seen this on other classes), and it states:

Improved Uncanny Dodge
At 5th level, the Assassin can no longer be sneak attacked except by a character with 4 or more total levels in classes that grant sneak attack than the character levels of the Assassin.

If I had Rogue 3, Warlock 9, Assassin 8, and Daggerspell Mage 10; would someone with 12 levels in class(es) that grant sneak attack be able to sneak attack me?
OR does "character levels" above count all my sneak attack classes (21 total levels of Sneak Attack classes), meaning that someone with 25 levels in class(es) would be able to sneak attack me?

[Born2BeWild]

keep in mind that this only works vs flank attacks