As far as i know , after processing the files will either be deleted or kept with the same name in the processed folder.
When you are saying that you are getting a different name, then I would suggest you to try tracing the listener and see what is changing the name. Watch out for properties like pyFileName and pyOriginalFileName under Log-Service-File class
In Test.1487272160154000.csv, the number is not the time stamp. It is the Unique ID and its value is stored in the pyUniqueID field. Open .rpt file generated in the same folder (processed folder) for more details regarding the time stamp and other property values.