Gen 46:27

46:27 seventy. The covenant family is represented by the symbolic number seventy (vv. 8–27 note), signifying a large and complete number (cf. ch. 10 note; Ex. 24:1; Ps. 90:10). In this group of seventy, the emerging nation of Israel was comprehended.

The Septuagint (Greek Old Testament) adds five sons and grandsons of Manasseh and Ephraim at v. 20 and gives a total of seventy-five, a reading followed by Stephen in Acts 7:14. Such variations occasionally occur in the Greek Old Testament, and we don’t always have the information necessary to explain them.