Why are only a few websites showing in the site list in Ui.Marketing?

Here is why you are seeing a small amount of sites in the reporting dashboard

These domains were determined by the ad platform as having served an ad. Often this is not passed back through reporting for premium inventory sources, so it may be represented as "undisclosed." The ad will have to have served enough impressions to each domain in this list for the site/domain to show up in this list.