carbon dioxide in liquid and gaseous phase with liquid water
At a given temperature a mixture of gaseous $\ce{CO2}$ and liquid $\ce{CO2}$ will have a particular pressure. Thus more liquid $\ce{CO2}$ doesn't mean that more $\ce{CO2}$ will dissolve in the water. 

Obviously liquid $\ce{CO2}$ has a lot more matter per unit volume than gaseous $\ce{CO2}$. So a little liquid $\ce{CO2}$ makes a lot of $\ce{CO2}$ gas.