'Fifteen' in the Bible

They took soundings and found it to be twenty fathoms; and a little farther on they took another sounding and found it to be fifteen fathoms.

Then three years later I went up to Jerusalem to become acquainted with Cephas, and stayed with him fifteen days.

The city is laid out as a square, and its length is as great as the width; and he measured the city with the rod, fifteen hundred miles; its length and width and height are equal.