GAM Backfill Revenue / 1000 Sessions is a Metric in Google Analytics under the DoubleClick for Publishers Backfill section
GAM Backfill Revenue / 1000 Sessions Definition: The total estimated revenue from backfill ads per 1,000 Analytics sessions. Note that this metric is based on sessions to the site and not ad impressions. If both AdSense and Ad Exchange are providing backfill ads, this metric is the sum of the two backfill accounts (DFP linking enabled and Hide DFP Revenue not enabled).
Data Analytics & Insights Google Analytics Metrics GAM Backfill Revenue / 1000 Sessions