The Passover seder at the start of the book represents freedom, the moon represents the continuity of the universe from one generation to another and numbers represent people exterminated during the Holocaust.
The book opens with the Passover seder that Hannah celebrates with her family. This represents their freedom to worship and celebrate as they wish, and is in sharp contrast to the denial of that freedom, as well as myriad other freedoms, during the Holocaust. That the celebration is of a seder is also symbolic. The author could have set the opening during a celebration of Hanukkah. Setting it during Passover underscores the freedom that Hannah’s family enjoys, as Passover celebrates the liberation from slavery in Egypt and the move towards becoming a united, free nation able to govern itself and celebrate as it wished.
Hannah looks out the window and sees that “a full moon was squeezed between two of the project's apartment buildings.” Later, when she is Gitl and living in a rural village, she sees that “the moon hung ripely between two heavy gray clouds.” The similar imagery of the moon hanging between two objects represents how the world is the same, even at the time of the horrors of the Holocaust and in modern day New Rochelle.
Numbers play a key role as symbols that represent individual Jews who were killed or survived the camps and the aggregate of six million. The brand on Grandpa Will’s arm, the tattoo that Hannah writes on her own arm in ink, the book's title and her trying to tell the others when she is transported back in time are all representative of the unimaginable numbers of people killed.
"No, Rabbi, six million in Poland and Germany and Holland and France and ... "
"My child, such a number."