'Addition' in the Bible

Now the cistern into which Ishmael had thrown all the corpses of the men whom he had killed along with Gedaliah was the one which King Asa [of Judah] had made [about three hundred years earlier] on account of King Baasha of Israel [believing that Baasha would lay siege to Mizpah]. Ishmael the son of Nethaniah filled it with [the bodies of] those who were killed.