R_DV is the residual, DV - P_DV.
And just a little more about V_DV since that can be confusing. The V_ variables are only calculated for decision trees since for all other models, the V_ and P_ columns would be the same. For decisions trees, V_ represents the proportion of validation obs in the same leaf as the current obs. that have a certain target level for a classification tree, or the mean of the target for the validation obs. in the same leaf as the current obs. for a regression tree.