# How to read solubility graph

The following table is showing the solubility of CO2 at different pressures.

However, I cannot figure out how to read this graph. The y-axis is molar fraction so that should mean that its value = mol CO$_2$/(mol CO$_2$ + mol H$_2$O). The journal that I got this graph from does not specify how many moles/what mass of water is used. Can I assume that it's 1 and that the y-axis is actually just the moles of CO$_2$