The file type table in Drive audit shows all of the files across your entire domain. Once you click on a particular file category, the filter will be applied and those files will appear in the Drive result table so you examine them in greater detail.
When it comes to Google Drive, GAT returns all document details for all users by default. You can filter by any selection range using the custom filters button.
Once these results are returned you can then add further filter criteria on top of the Type filter.
Note: This search will return files of type Spreadsheet and which are also shared out of your domain.
Remember if this is a frequent search, you can ‘Apply & Save’ it.