Commentary for II Samuel 24:3

Their [current] number. [Yoav meant with] the word כׇּהֵם to convey that their amount should double and the second word וְכָהֵם, to convey a second doubling to have now a total of four times [the original population] and then to again double the [new] total for one hundred times.¹For a total of two hundred times the current population. It follows that Yoav's blessing was more then Moshe's who said, "One thousand times you [current] number".²Devorim 1:11. Furthermore, Moshe's blessing was only [to take effect] a long time [into the future] but Yoav's was intended [to take effect] immediately as it says [here], "[With] my master, the king's eyes [being able to] see it."