Explain Annemarie's joke about the butter.

Annemarie and her mama are uneasy and nervous because of the plans to help the Rosen family escape. Mama tells Annemarie that Uncle Henrik has saved a small amount of butter for them. Annemarie asks her mama what Uncle Henrik has saved the butter from. Annemarie jokes with her mama, asking if the Nazi soldiers are trying to "relocate butter." This also refers to the fact that the Nazis are relocating Jews from Denmark. Mama then says that the Nazis have been taking the butter from the farmers to feed their army. She jokingly tells Annemarie that they might seize the small amount of butter that Uncle Henrik has set aside. Mama, Annemarie, and Kirsti laugh at the thought of soldiers seizing such a small amount of butter. Essentially, they are laughing to keep their minds off of the troubles they are facing.