Leviticus 27:18

But if he sanctify his field after the Jubilee, after some years had elapsed, then the priest shall reckon unto him the money according to the years that remain, even unto the year of the Jubilee, and it shall be abated from thy estimation. In the case of a field of barley, for instance, if twenty years still remained till the nest Tear of Jubilee, then the person concerned would have twenty shekels to pay, plus the one-fifth which was added for the sake of compensation, if it was so arranged.