I noticed it's strongly recommended not to "Delete files that don't exist in source any more", due to possible accidental deletion of files by viruses or malware on PC. Usually viruses and malware attack and destroy more than one single file and most of the time it destroys hundreds of files. Is it possible to set the task so that it doesn't proceed in deleting files only in case there are hundreds of files (or more than a fixed number or files, or more than a certain percent) missing? I think this would be much useful, would avoid virus-caused deletion and would reduce disk space needed for backup files.