How is the expiatory payment (fidya) calculated for delaying the making up of Ramadan days for years due to ignorance of the ruling?

Whoever delays the fasts due from Ramadan without a valid excuse until the next Ramadan begins, must make up those fasts (qada') and pay an expiation (fidyah) for each day he delayed. If he has already made up what was due, then the fidyah remains an obligation upon him, which is: feeding one poor person for each day, equivalent to 750 grams of rice or similar staple food. The fidyah does not multiply with the number of years; rather, it is a single fidyah regardless of how long the making up of the fasts was delayed.