English: In the total you find seventy, but in the detailed count you find one fewer ... This is Yocheved, who was conceived on the journey and born between the walls.
On the daf / in context: Adding Yosef’s two sons born in Egypt brings the household to the traditional seventy.
Type of Learning
Derash on the verse (midrashic accounting) — not a formal named middah of the 13.
What Is Learned
The house of Yaakov that entered Egypt numbered seventy souls.