You can show a single, aggregated number. It is good for tracking a specific number, and it is good for using it in Dashborads.
Value - Assign a data column you want to show. It can be in any data types.
You can rename the chart then the same name comes up as a caption.
You can use the Custom Function feature to define your own aggregation function. See Custom Function for the detail.
Default Value - The default text value used when the data is NA. The default is ''.
Take a look at Layout Configuration on how to configure the layout and format.