He worked four years and two remain, he should give him two, according to his years - עבד ד' ופשו ליה תרתי ניתיב ליה תרתי כפי שניו
Summary:
According to רש"י the question was; let us say the פסוק is not discussing a case of השביח or הכסיף. However, תוספות maintains that the question is that regardless whether הכסיף or השביח, the עבד should pay a price depending on whether his term now is closest to the כניסה or יציאה.
Whoever acquires an Eved Ivri; it is as if he acquired a master for himself - כל הקונה עבד עברי כקונה אדון לעצמו
Summary:
The קונה אדון לעצמו is in a case where the master has only one of a kind (like one pillow), he must give it to his servant to fulfill the טוב לו עמך, and not act כמדת סדום.