Recent research has acknowledged young children's potential to engage in data handling activities and create their own representations. However, our knowledge on children's graphical signs produced during data representations and the way they are utilized is poor. Highlighting the critical importance of signs as cultural tools for mathematical learning, this study focused on the components of the original data representations which emerged from child-initiated data investigations. Analysis of children's artefacts revealed five kinds of inscriptions and four kinds of information included in their data representations. The insightful way of utilizing their inscriptions demonstrated how the young learners, apart from inventing their own graphical signs, adapted broadly accepted symbols to the contextual and communicational requirements of their inquiries and made them part of their personal toolkit for handling data tasks. These aspects of their meta-representational knowledge are discussed through a sociocultural lens, while implications for research and practice are also suggested.