If there are still many years ⌞until the jubilee⌟, you will pay more for it. If there are only a few years ⌞until the jubilee⌟, you will pay less for it because he is selling you only the number of crops.
Then he and his buyer must take into account the number of years from the year he was bought until the year of jubilee. His sale price will be adjusted based on the number of years he was with his buyer, like the wages of a hired worker.
If there are only a few years left until the year of jubilee, he must take them into account. He must refund from his purchase price an amount equal to those years.