There have been many efforts to measure pedagogical content knowledge with multiple-choice survey instruments, but little is known about how different types of items contribute. In this study, we examined interviews with 9 Grade 4 teachers to develop a deeper understanding of how teachers select pedagogical representations in the context of a survey assessment. Our analysis revealed two broad themes: representational justification (focused on how teachers interpreted features of the representation) and contextual justification (focused on how teachers considered their students and their own perspectives and experiences). These results indicated that content and pedagogical knowledge were highly intertwined in teachers' work on these tasks. However, the results also identify limitations for using this item type to measure teachers' pedagogical content knowledge in mathematics. Implications are discussed. [For the complete proceedings, see ED630060.]