i believe it is telling you that you died 3 times while using the zipline, although i think i have heard it is possilbe to by from ziplines, grappling hooks etc.
Hmmm, would it count when some bastard gets to the other side grabs it without checking no-one is using it? Obviously they always deliberately wait until you are having a sip from a drink or something grab it, just to make sure you don't get time to hit 9.