Report Record Count Changes When Show Details Is Hidden or Exposed in Reports

Why the Record Count Changes When Details Are Hidden
When report columns are hidden (Show Details is disabled) and the report does not contain references to any parent or child of the target object — such as filters, summaries, or groupings — then any relationship requirement defined at the Report Type level is ignored. This causes records that would normally be excluded to appear in the report, increasing the count.

Example Scenario: Opportunities Report with Account Columns
Suppose you create a report on the Opportunities object and add columns from the Accounts object.

• Reports require that displayed results have relationships between all objects that have columns shown on the report.
• By adding Account columns to an Opportunities report, you mandate that any records displayed must be associated with an Account record.
• If you hide the details of this report and do not update your report references (filters, summaries, groupings) to capture this requirement, then the requirement that an Account be defined is ignored.
• As a result, Opportunity records without an associated Account will appear in the report, increasing the record count.

Additional Notes

• This behavior does not occur for the "With or Without" relationship dynamic available with Custom Report Types. However, objects within Custom Report Types relying on the traditional "With" relationship are still impacted.
• Records not associated with the objects referenced by a report's columns will not appear on the report. Removing the columns that reference other objects will not change this behavior or add the missing records to the report.