Occasionally a ballon message will pop up in the bottom right-hand corner of your screen which says "Unknown file extensions require a decision for backup"
This is telling you that Version Saver has come across some files with extensions that it doesn't recognise. It needs you to tell it whether these files should be backed up or not.
Clicking on the ballon will display the Version Saver configuration window in which you will see that the "Undecided" file extension list has one or more entries
Drag and drop these entries to either the "Back Up" or "Don't back up" lists, depending on whether you want to save versions of the files with those extensions or not.
Once this has been done, you will not be prompted about those particular file extension(s) again.
If you don't click on the balloon, it will disappear after 15 seconds or so, or you can deliberately click the X on the balloon to dismiss the message
The ballon will appear briefly every 5 minutes or so, until you have taken action on the extensions as described above.
