What is the meaning of the phrase "You have given us more than half, and you have done well" which was said by the family of Zayd ibn Harithah - may Allah be pleased with him - to the Messenger of Allah, peace and blessings be upon him, and is its wording correct?

The phrase "قد زدتنا على النَّصَفِ وأحسنت" (You have given us more than what is just and done well) appears in more than one source with the ضبط (vowelization) of "النَّصَفِ" as an open ن (nuun), a shaddah on the ن (nuun), and an open ص (saad). Its meaning is: giving what is due. That is: You have given us more than what is due, and you have done well. So, "أنصف" (ansafa) means to take what is due and to give what is due, and "النَّصَف" (annasaf) is the verbal noun derived from that. It is as if its derivation comes from giving half and being content with it.