Different versions will have different pagination. The quote can be found in the midst of chapter 5. In this chapter, one of the significant moments is when Bruno and his father speak about the condition of life in "Out- With." Bruno's father seeks to make the lines clear between Bruno and his life and those who live "in the striped pajamas." The quote occurs at a point when Bruno's father's words will be prophetic. They will not scare Bruno from interacting with the life that is "on the other side." Rather, they seem to be providing a sense of challenge to him, the element of a "great adventure."
It is in this light where the line happens in the text. Father's "advice" to Bruno in the form of how to view life on both sides of the fence are meant as a statement of what is, a description of the existing condition at "Out- With." However, Bruno is an agent of change. The entire reason he has sought out his father is out of a sense of seeking answers. Father's words that are found in chapter five are a representation of what is, while Bruno is envisioning what can be or what might be. In this light, Father's answers do not end Bruno's sense of curiosity and inquisitiveness. Rather, they only fuel such sensibilities.