What does Deuteronomy 3:11 mean?

Og, king of Bashan, was the last of the Rephaim. His bed was made of iron and is still in Rabbah of the Ammonites. It was over thirteen feet long and six feet wide. Deuteronomy 3:11 - Modern Text Bible

(Og is described as a giant, the last of a legendary people. The mention of his huge iron bed underlines his size and the reality of his defeat.)