Having summary fields provides a quick overview of the data in the table. It can show the total count of records, the sum of certain fields, the average of numerical fields, and other useful information. To set this up, you need to go to:
Portal Tables
Click on a linked record field
Summaries section
Add field in Summary Fields
Once you have added a summary field, you can toggle on/off Show Summary Field Titles. Turning off the field title allows you to either not have a title at all, or to provide your own custom title within the field's formula itself:
e.g. "Total: $" & SUM(values)
Summary fields are taken from the user table, and the values displayed in the summary are not affected by the records displayed in the grid. Instead, the values are pulled directly from the users table. Since the field comes from the users table, this feature is not supported in Shared Views.