what does hannah learn from aunt eva after returning to her real life?

At dinner Hannah notices the prisoner tattoo on Aunt Eva's arm and recognizes it. She explains the numerical relevance of the number to Aunt Eva, who confesses that when she was young she was known by another name: Rivka. After coming to America many of the survivors changed their names. Grandpa Will, Eva's brother, was known as Wolfe before. She tells Hannah that in addition to them, only Gitl and Yitzchak survived the camps. They both moved to Israel where Yitzchak became a politician. Gitl started a charity to help survivors of the Holocaust reunite with their families. She named the charity CHAYA, after her niece who perished in the camp.