One of two ways to view your extensions data within the 'Extensions' page. Note that the 'Extensions' page will first display the summary cards, so you must click the table icon at the top, click the 'Associations view' drop-down, and select 'Extensions view'.
In '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 '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 'Associations view'.