This article reports on an exploratory study of quantitative data use situated in families' management routines while taking care of a child with Type 1 diabetes (T1D). T1D treatment requires frequent measurement and recording of numerical data about blood sugar concentration, nutritional intake, and insulin dosage at the child's home, at school, and at other activities. We analyze coordination work between family members and others involved in the care of children with T1D using the lens of distributed cognition, and we introduce the notion of a data catchment to refer to the pathways of data flow and information storage within and between multiple agents and spaces. Interviews and observations reveal three main features of storage and use in data catchments: First, there is a great variability in how data move and are retained to enable communication between family members and others. Second, families tended to focus more on individual data points and less on aggregate readings despite some indications of ability to narrate through aggregate readings. Third, families engage in recurrent conversations and sometimes use novel artifacts to make numerical values meaningful to children with T1D. Implications for understanding this space of practice as constituting a data catchment are discussed.