If mult-kill flag is true, the ap gets 0 charges regardless of the "charge value" of the kill is.
Take what I think would be an example -
kill a cabal leader get 7 charges, kill another person get 1 charge, run back and kill the same cabal leader at their pit just as they unghost - get another 7 charges.
You can probably repeat this several times (I've a hunch cabal leaders are never worth 0 charges regardless of how much they are a punching bag or not unless they are high heralds).
But, if you don't kill someone in between, you will get 0 charges even though the cabal leaders worth is still 7 charges.