Translations
Their total number, together with their brothers trained in singing to Yahweh—every one of them skilled—was two hundred and eighty-eight.
Their total number, together with their brothers trained in song to YHWH—all who were skilled—was two hundred and eighty-eight.
So the number of them, with their brethren that were instructed in the songs of the LORD, even all that were cunning, was two hundred fourscore and eight.
Together with their relatives, who were all trained and skillful in the songs of the LORD, they numbered 288.

