When you work with titles, labels and mouse-over inside a TARGIT object, you can actually do calculations inside the title, label or mouse-over dialogue.
You do it by clicking advanced settings (which is the gear symbol next to your title, label or mouse-over drop-down:
and then choose to add a numeric value:
This numeric value will then have it's own "sub" dialogue where you can add calculations in the dialogue (in the example below the minimum of the column is calculated):
Watch this tutorial to see an example of creating a statistical overview of data in the title of a graph: