'Unit' in the Bible

Now there was a wall surrounding the outside of the temple. The measuring rod in the man’s hand was six units of 21 inches; each unit was the standard length plus three inches. He measured the thickness of the wall structure; it was about 10 feet, and its height was the same.

“These are the measurements of the altar in units of length (each unit being the standard length plus three inches): the gutter is 21 inches deep and 21 inches wide, with a rim of nine inches around its edge. This is the base of the altar.