Percentages have proven to be a challenging concept in school mathematics. At the surface, a percentage is merely a rational number, representing a ratio between a number and 100. At the conceptual core, however, a percentage is sensitive to the context, making sense with respect to a network of related quantities. In the effort of the authors to engage their students in the conceptual exploration of rational numbers, they noticed a milk bottle label and posed a few questions about the use of percentages in this context. Simple as it is, the milk label gave a meaningful lens to explore the dynamics of percentage use in context. In this article, the authors analyze the Milk Fat problem and the diverse responses of their students (in this case, prospective elementary teachers) because their responses relate to perspectives of additive and multiplicative reasoning and literacy. The authors further discuss the impact of intervention and the persistence of additive reasoning. They invite readers to try the problem with their own audiences.