When you create a Content Lifecycle policy, the value you see in Matched Files is indicates the number of files under management for that policy, not the number of files affected by the policy once implemented. The Impact in the Next 30 Days value is the number of files that will be affected in the near term.
If you would like more detail about when the policy will actually take action on the files, you can view and export the list of files subject from the policy by clicking on the number listed under the Matched Files or Impact in the Next 30 Days or by clicking on the download icon under the Files by policy widget on the Content Lifecycle dashboard, and each file will have an "expected trigger date" value that shows when the policy will take action on each file.