How do Ike and McCaslin learn the dark truth of their family's history on the plantation?

When Ike learns that he hand McCaslin have inherited this large chunk of land, they spend the day reading through old ledgers from their father's plantation. There, they learn the dark truths of their family history with slavery and feel disgusted to know they are apart of this history even though they were born generations after slavery was abolished. They vow not to perpetuate these crimes against humanity and to do whatever they can to reverse their family's negative effects on race relations.