What made Annemarie realize that her father was speaking in a code to her uncle? What was their conversation really about?

Papa wants to bring the whole family Henrik's home, but Mama insists that if Papa skips work, he will make the Germans even more suspicious. Later that day, Annemarie hears Papa speaking on the phone in code to Uncle Henrik. He tells Henrik that Mama is bringing him one carton of cigarettes—that is, one Jewish refugee—today, but more will be coming. At this time, though, Annemarie does not yet fully understand the code.