What is the share of a half-free mother when accompanying a half-free daughter?

Primary text

If a free mother is present with the half-free daughter, the mother receives one-fourth (al-rubʿ). This is because the daughter's freedom (being half free) prevents the mother from receiving her standard one-sixth share; thus, half of the daughter's freedom prevents half of the mother's entitlement, leading to the mother receiving one-fourth.