Is it true that the throwing of Jamrat al-Aqaba al-Kubra (the Great Aqaba Pillar) is not counted among the two days mentioned in Surat al-Baqarah, "But whoever hastens in two days, there is no sin upon him"? If so, what is the expiation for someone who threw Jamrat al-Aqaba al-Kubra only once based on this understanding?

Throwing the pebbles (ramy al-jamarat) is one of the obligations of Hajj. The large jamarah is stoned on the Day of Sacrifice (Yawm al-Nahr), and the three jamarat are stoned on the Days of Tashreeq, starting with the smallest and ending with the largest. Your father owes a dam (expiatory sacrifice) for not stoning on the second day, which is a sheep to be slaughtered within the Haram (sacred precinct) and distributed to its poor. The sin is lifted from him due to his ignorance.