If you would like to show a different aggregation on your totals vs what aggregation you have in your chart (bar/text etc), you can right-click on your green pill (measure) and change aggregation to i.e. MAX.

Remember to format the title to the appropriate value to make sure your users see the change in the view.

First build i.e. a Text Table with your measures, in this case all are SUM.

Then right click/open the menu to change through “Total using (Automatic)” to one of the available aggregations. In my example I’m changing to Maximum.

Next step, right-click on “Grand Total”, choose Format.

Then on the “Format Pane” -> replace the “Grand Total” text to “Maximum value” or something appropriate to your data.