Rashi on Numbers 26:59/רש"י על במדבר כ״ו:נ״ט

1אשר ילדה אתה ללוי במצרים WHOM HER MOTHER BORE TO LEVI IN EGYPT — she was born in Egypt but was not conceived in Egypt; when they came “between the walls” (within the confines of Egypt), she gave birth to her, and she (Jochebed) made up the number of seventy; because in the enumeration of them (Genesis 46:8—27) you will find only sixty-nine (Numbers Rabbah 13:20; cf. Rashi Genesis 46:15).