John Gill Commentary Leviticus 25:52

"And if there remain but few years unto the year of jubilee, then he shall reckon with him; according unto his years shall he give back the price of his redemption." — Leviticus 25:52 (ASV)

And if there remain but few years until the year of jubilee ,
&c.] Fewer than what he has served, then the less is given for his redemption: thus, for instance, in the above supposed case, if he has served fifteen years, and there remain but five to the year of jubilee: then he shall count with him, [and] according to his years shall he
give him again the price of his redemption ;
as in the fore mentioned case, he shall give him five pieces of money; and thus the law of justice and equity was maintained between the buyer and seller, the purchaser and the redeemer: in a like righteous manner the people of God are redeemed by Christ.