To Summarize Information in Report Columns

Open the Reports dialog (Drawing > Analyze > Reports).
Select Summarize for the desired report definition.
Select the Add rule button. As you click Add it will sequentially add columns with pre-filled rules.
Select the desired columns from the columns drop-down menu.
In the Sum drop-down menu, select the desired method.
Add more columns using the add button, if needed.
Select Preview results in the Reports dialog.

You will see a preview of the Report generated with the summary displayed at the bottom of the report. If you place the report as a table in model, you will see the summary as the last row in the table.
Note: You can choose to hide the summary in the report by selecting Hide in Reports dialog > Properties > Summary row.

Figure 1. Report placed as table in a model