Folder action acts on files not specified in the workflow
A Folder Action workflow will give you every file when a change is detected in the specified folder, including ones you are not interested in. 

Your problem is with Get Specified Finder Items. It just adds items to the list of files to process. It doesn't filter anything!

Use the Filter Finder Items action instead to filter the list returned by Finder. You can do it any number of fields/options including name, extension and type.