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Understanding How Reports Are Displayed on a Dashboard

Reports shown in dashboards have two different defaults for the number of columns shown, based on the layout of the dashboard. 

If the report is selected for an area of the dashboard that takes up the full width of the dashboard, then by default, all fields are shown.

If instead, the report is selected for an area of the dashboard that takes up less than the full width of the dashboard, then by default only the first field of the report is shown.

You can override these default settings in the report builder for each report. In the advanced options on the column for the field, select 'show this column when on a Dashboard' on each field where you want to override the default settings.