If partial time for Istibra' passed before the slave girl's manumission, is a new Istibra' required?

Primary text

If some portion of the required Istibra' time elapsed before her manumission, she must complete the remaining time afterward. It is not obligatory for her to start a new Istibra' period from the beginning, because the requirement for Istibra' was established by the purchase, not by the emancipation, thus the count begins from when its cause became effective.