1 . The file name “_1467740774851” is just a unique identifier for the file that you are downloading.
2. To change the file name, you can manually rename it, or through your browser settings select ‘Ask where to save each file before downloading’.
It is unique timestamp which Helical Insight adds whenever you download anything from it. It uses this format like _. If the report name is empty then you get that type of file name.
You can give specific file name for dashboard, there are 2 ways,
Server end : Enable a setting which forces the end user to provide the name of the downloaded file. You can do so by changing the tag called false (set this to true).
Report end : You need to set reportName variable before exporting this variable and that will do the trick.