Hi, what kind of notification?

Hi, good question, this is how we understand this feature:

RealTimeSync process continuously runs in the background, yes it starts automatically when PC starts, and it also continues to run afterwards independently.

Sync delay only defines actual synchronization frequency to spare your CPU/HDD/SSD/Network resources and avoid doing double work e.g. while you work on heavy files on the main drive/partition/folder.

Process monitors changes, and when the timer reaches predefined delay without any further changes activities, it runs the sync procedure automatically in the background. Then the new cycle runs, but if there are no changes made, there will be nothing to sync.

In simple terms, let us consider an example: you work on a file, then you save it. Delay timer starts, and starts counting to 10: 1, 2, 3, 4… But, 5 seconds later you do another change and save the file again. Delay timer resets, and starts counting again to 10. If you do not make any further changes this time in that predefined delay interval, sync process will run in the background and synchronize the file with remote drive/partition/folder.

This is an excerpt from the FreeFileSync manual, hope it further clarifies this matter:

RealTimeSync receives change notifications directly from the operating system in order to avoid the overhead of repeatedly polling for changes. Each time a file or folder is created/updated/deleted in the monitored directories or their sub directories, RealTimeSync waits until a user-configurable idle time has passed in which no further changes were detected, and then runs the command line. This makes sure the monitored folders are not in heavy use when starting a synchronization.