What is the expiation for masturbating during the daytime in Ramadan—given the uncertainty and ignorance of its ruling—for someone whose age was between 13 and 15 years, and was he considered an adult and accountable at that time?

The signs of puberty are known as the emission of semen while awake or asleep, the growth of coarse pubic hair, or reaching fifteen lunar years of age. Whoever exhibits one of these signs becomes accountable (mukallaf). The fast of one who masturbates during the daytime in Ramadan is invalidated by the emission of semen, and they must make up the days they missed if they knew of the impermissibility of masturbation. However, if they were ignorant, then there is nothing upon them. If they were doubtful about the impermissibility of masturbation, then the fast is invalidated and making it up is obligatory. Whoever delays making up their fast without an excuse until another Ramadan begins, must pay expiation (kaffarah), which is feeding one poor person a mudd of food for each day. However, if the delay was due to an excuse, there is no expiation upon them. Whoever is ignorant of the number of days they missed should make up what they predominantly believe will clear their conscience.