The title says Joab "killed twelve thousand of Edom in the Valley of Salt" (60:1). 2 Samuel and 1 Chronicles tell of the Valley of Salt with other names and numbers. Which is right?

The title is "For the Chief Musician. To the tune of “The Lily of the Covenant.” A teaching poem by David, when he fought with Aram Naharaim and with Aram Zobah, and Joab returned, and killed twelve thousand of Edom in the Valley of Salt" (60:1). 2 Samuel tells of David and "Hadadezer the son of Rehob, king of Zobah" (2 Samuel 8:3), and then says, "David earned a reputation when he returned from striking down eighteen thousand men of the Syrians in the Valley of Salt" (2 Samuel 8:13). 1 Chronicles says, "Moreover Abishai the son of Zeruiah struck eighteen thousand of the Edomites in the Valley of Salt" (1 Chronicles 18:12). So the three name Joab, David and Abishai; they say Edom, Syrians and Edomites; and they give twelve thousand, eighteen thousand and eighteen thousand. The chapter on 1 Chronicles 18 sets the same three verses side by side, and the chapter on 2 Samuel 8 sets out the other differences between those two books. The Bible gives them without explaining how they fit together, and these notes don't explain them either. They don't add to what the title says, or explain its tune.