Read the words, forget about unstated "other meanings".
Rigga is right as ever, the sentence is crystal clear. Replace at 1500 hours, unless you find (in one of the 100 hour inspections) that it exceeds the stated tolerance, in which case it must be replaced immediately.
To put it another way, without a replacement cable the aircraft is unserviceable if (a) the cable has more than 1500 hours or (b) on the last 100 hour inspection it was found to exceed the allowed tolerance.
There is no leeway on the 100 hour inspection either, as I understand it. Hmmm, I wonder how many aircraft fly with that one overdue? Can Rigga comment?