The Key Metric with a following column for the percentage between the campaigns, depending on the metric data selected to display in the table. If the Second Metric selected, the metric data is displayed in the last column of the table.
In the Report Options the settings can be changed to hide or show the chart, table, row titles of the table, percentage column, color indicators and the Totals Row.
The Totals Row is calculated amount only for the values that are not with % units.
The percentage value is based on the Key Metric selected for the metric data in the Report options. The percentage is the metric data share value between the campaigns.
In this case the Key Metric was Conversions and the share percentage of the conversions between the two Google Ads campaigns. The second metric is Cost.