How reports calculate percentages
The default calculation of the audience size, both in the aggregate campaign report and for individual publication reports, has been updated to account for scenarios in which a publication has been sent to an endpoint that is open to all members of an organization. These publishing scenarios often result in very large audiences, which can cause the denominator in the percentage of the Unique Viewers calculation to be confusing, even when it's correct.
In cases where an audience is not explicitly defined and publications can be widely viewed within an organization, Amplify reports show a count rather than a percentage so that the data is easier to understand.
Hidden members
If you send a publication to a distribution list that contains hidden members or groups, these hidden members won't reflect in your reporting denominator. This means that your denominator might be different than you expect in your reporting view.
Dynamic groups
If you send a publication to a dynamic group, the group won't be able to expand. As a result, the group's members won't be included in your reporting denominator.
Example
The total audience is calculated as the sum of the members of the groups with rights to see the published publication. The user count is determined by adding the Microsoft Entra ID users with permissions to the published publication. If this number is very large, the percentage of unique viewers can show as very small, such as a tenth or hundredth of a percent.
For example, a communications manager creates a publication geared towards their organization's sales team. In the interest of transparency, they share it to a SharePoint page that is accessible by all 521,000 employees of their organization. The sales team, which is the intended audience of the publication, consists of 3,000 people. If the publication is viewed by 2,600 people, the communications manager may expect to see a high percentage. However, since all 521,000 employees have access, the percentage of viewers would only show as 0.5%.