If you've correctly specified inventory sizes in your proposal line item, there should be a one-to-one relationship between creatives in Display & Video 360 and the creative placeholders in Ad Manager.
You can then generate creative reports based on these placeholders.
Therefore, when you run a report from the line item level, results may be unclear due to the size value included in the default naming convention. We recommend including the "Creative size (delivered)" dimension for accurate delivery reporting by size.
The exception is video master/companion campaigns. While you can run video master/companion campaigns, Ad Manager does not collect metrics on companion ads hosted in Display & Video 360. As a result, Ad Manager reports won't capture delivery for companion ads in reporting for programmatic campaigns.
