John Gill Commentary Leviticus 25:50

"And he shall reckon with him that bought him from the year that he sold himself to him unto the year of jubilee: and the price of his sale shall be according unto the number of years; according to the time of a hired servant shall he be with him." — Leviticus 25:50 (ASV)

And he shall reckon with him that bought him That is, either the man himself should reckon with him, or whoever undertook to redeem him.

from the year that he was sold to him unto the year of jubilee and so count how many years he had served, and how many were yet to come; and by this it appears, that one thus sold was not released at the end of six years, or the sabbatical year did not free him.

and the price of his sale shall be according to the number of years whether more or fewer, as after explained.

according to the time of an hired servant shall it be with him the time of service he had served his master shall be reckoned, as if he had been hired for so much a year; and according to the number of years he had been with him, so much per annum was to be deducted from the original purchase, and the rest to be made for his redemption to him that bought him.