They and their buyer are to count the time from the year they sold themselves up to the Year of Jubilee. The price for their release is to be based on the rate paid to a hired worker for that number of years.
References for Leviticus 25:50
If many years remain, they must pay for their redemption a larger share of the price paid for them.
If only a few years remain until the Year of Jubilee, they are to compute that and pay for their redemption accordingly.
References for Leviticus 25:52
They are to be treated as workers hired from year to year; you must see to it that those to whom they owe service do not rule over them ruthlessly.
References for Leviticus 25:53
“ ‘Even if someone is not redeemed in any of these ways, they and their children are to be released in the Year of Jubilee,
for the Israelites belong to me as servants. They are my servants, whom I brought out of Egypt. I am the LORD your God.
References for Leviticus 25:55