What is the ruling concerning the freedom of a Mukatab proportionate to the amount he has already paid?

Primary text

It is narrated from Ali, may Allah be pleased with him, that he is freed to the extent of what he has paid. Furthermore, a narration from Ibn Abbas, may Allah be pleased with them both, states that the Prophet, peace and blessings be upon him, said that if a Mukatab attains a legal punishment (Hadd) or inherits wealth, he inherits according to the portion he has paid, and the Mukatab must pay the remainder according to that paid proportion. Umar, Ali, and Al-Nakha'i stated that if he pays half, there is no servitude remaining for him.