What are the connotations of "Vechishav im Koneihu"?
Rashi (on Pasuk 48) and Seforno: In spite of the fact that the Pasuk is speaking about a Nochri who is under our jurisdiction, one is obligated to make an accurate assessment of how much the Eved Ivri owes his master and not force him to release his Eved free of charge or for less than the full amount owing.
What are the connotations of "ki'Yemei Sachir Yih'yeh Imo"?
Rashi: One reckons how much he paid and divides it by the number of years until the Yovel. 1 If they then redeem before the Yovel, they deduct the years that he worked, and return the balance to the Nochri.
Rashi: If for example, the Nochri bought him for twenty Manah twenty years before the Yovel - then he bought each year for one Manah, like a hired worker. Assuming they then come to redeem him after five years, they deduct five Manah and pay the Nochri fifteen Manah.