Note that as per
Help > Quick Start > Understanding Backup and Synchronization
the difference between Backup & Mirror is that the former won't delete any files on Destination (that don't exist on Source) whereas a Mirror (Right) will. Given it's just deleted 5152 files (because you told it to), I hope you didn't need them for anything...
Help > Quick Start > Understanding Backup and Synchronization
the difference between Backup & Mirror is that the former won't delete any files on Destination (that don't exist on Source) whereas a Mirror (Right) will. Given it's just deleted 5152 files (because you told it to), I hope you didn't need them for anything...