What does Deuteronomy 2:19 mean?

When you get close to the Ammonites, don’t bother them or pick a fight. I’m not giving you any of their land. I’ve already given it to the descendants of Lot as their own place.’ Deuteronomy 2:19 - Modern Text Bible

(God instructs Israel not to attack the Ammonites, because their land is not for Israel but for Lot’s descendants.)