One of two ways to view your extensions data within the extensions page.
In the extensions view, each row contains data that is specific to a single extension, aggregated across all its associations. Each extension is listed once, and fills its own row. Use the extensions view to compare the performance of one extension with another.
Keep in mind that any time you create an extension, such as a callout or structured snippet extension, you can associate it to any of your ad groups or campaigns, or to your entire account. This means that a single extension can have multiple associations. To view these associations, switch to the associations view.