When the Spend by impressions delivered toggle is off, spend on the dashboard will show Total spend for each line item and campaign. Total Spend is taken directly from the numbers entered during campaign setup. For a completed campaign, spend will always be displayed as Total Spend.
When the Spend by Impressions Delivered toggle is on, we will calculate the spend to date based on the total impressions delivered. This calculation is (Impressions/1000) * CPM. For a completed campaign, spend will always be displayed as Total Spend.
Note: If your campaign has over-delivered impressions beyond the impression goal, you will never see a spend number higher than the total spend you entered during campaign setup.