Summary field formatting
Specify the format expression for the server-side summary fields for this field.
The Summary field formatting property can be used to define the formatting expression for the calculated Total, Count, Average, Maximum, or Minimum summary values for a field.
You can define format expression for the server-side summary fields. For example, to round the average to 2 decimals, specify:
Some summary calculations are not available for some field types. Available types are based on the data type of the field.