If you want to select the optimization and out-of-sample data sets graphically, click on the Use graph button.
The data grid allows you to select the optimization and out-of-sample data sets totally independent of one another. For example, you can optimize on the most recent data and apply the model to older data. Click on either the optimization set or out-of-sample set and then mouse click on the graph to select the data you want to include in the specific set.