Parallel
Numbers 21:13
Brenton's English Septuagint · Berean Standard Bible
And they departed thence and encamped on the other side of Arnon in the wilderness, [the country] which extends from the coasts of the Amorites; for Arnon is the borders of Moab, between Moab and the Amorites.
From there they moved on and camped on the other side of the Arnon, in the wilderness that extends into the Amorite territory. Now the Arnon is the border between the Moabites and the Amorites.