How to adjust TPR / TNR for oversampled data?

[jbencina]

My original dataset has a proportion of Y = 90% / N = 10%. Using the Sample node, this was made 50% / 50% before running through a Decision Tree node. I understand the Decisions node allows for adjustment of Profit based on prior probabilities, however I read that classification rates are not adjusted. 

How do I adjust my True Positive Rate / True Negative Rate in this scenario given the oversampling and prior probabilities?

[Damien_Mather]

adjacent to the decision weights tab in the same data source step is a target priors tab for just that.