What is the ruling if a master revokes the manumission of only half of a slave he had fully designated for manumission?

Primary text

If a master designated the entire slave for manumission and subsequently revokes the designation for half of the slave, the revocation is valid, provided that the master is generally considered capable of revoking the entire Tadbir. This is based on the principle that just as it is valid to designate half the slave for Tadbir initially, it is valid to revoke the Tadbir for half of the slave.