The pop up is used to get details of the Dataset object at first execution of the report in Report Designer. If the saved report definition has dataset info, then the selected items are shown in the pop up, by default. Report Designer supports to dynamically change method, class, and the namespace of the business object, so the pop up shows up with all default selection items. Once the report has been saved with dataset info then the dataset info code will be generated in the report definition. Please refer to the below screenshot for the saved dataset information.
However, you can edit the report definition of the report in code behind and you can insert the above highlighted code. Please refer the following KB for editing the report in code behind.