How did elie become A-7713 in Night?

In the book "Night" by Elie Wiesel, Elie becomes A-7713 after he and his father are deported to the Buna labor camp. Upon their arrival, they are assigned prisoner numbers by the Nazis, which serve as their identification in the camp. Elie's original name, Eliezer, is replaced by the number A-7713, effectively reducing him to a mere number, dehumanizing him, and stripping away his individuality.