Dark Dreams of Furiae - a new module for NWN:EE! Buy now
I checked http://iesdp.gibberlings3.net/scripting/triggers/bg2triggers.htm
, and had a look at the LevelParty trigger.
I think that description is wrong.
The game gets the max level for each of your characters(dual/multi class chars contribute only the highest of their classes), and then divides that number by the number of characters in your party. It then compares it to the argument to LevelParty()
So LevelParty(8) for a party of Fighter:6, Mage/Thief:4/5 and Cleric: 5
will look something like
(6 + 5 + 5)/3 = 5
return 5 == 8