We address the question: How can a student's conceptual transition, from attending only to singleton units (1s) given in multiplicative situations to distinguishing composite units made of such 1s, be explained? We analyze a case study of one fourth grader (Adam, a pseudonym) during the course of a video recorded cognitive interview. Adam's case provides a glimpse into this process, as he proceeded from solving a prompt-less version of the multiplicative situation to two versions that gave gradually more explicit hints for those two types of units. We postulate an inferred process in which Adam reflected on the relationships between his counting actions (of cubes and towers) and the effect of those actions being different numbers pertaining to different units. We discuss the theoretical importance of explaining this transition and its practical implication of understanding whole number multiplication (e.g., array). [For the complete proceedings, see ED606556.]