macOS sometimes creates files that are hidden in the Finder and may cause confusion when mentioned in a sync error or listed in the sync confirmation dialog.

• .DS_Store and .localized are system files that can appear inside any directory. It is recommended to exclude these system files with a Filename filter or by excluding hidden files altogether. If listed in the confirmation dialog, you can right-click them to open the context menu and select Add all files with the same name to the filter.
• .DocumentRevisions-V100, .Spotlight-V100, .TemporaryItems and .Trashes are system directories that appear at the root of an external volume. SyncTime doesn’t have enough privileges to access these system directories. Instead of selecting the root directory as the destination, it is recommended that you create a dedicated directory and select it as the destination. Alternatively, you can exclude these system directories with a Filename filter or exclude hidden files altogether. If listed in the confirmation dialog, you can right-click them to open the context menu and select Add selected files to the filter.

Tip: you can toggle the display of hidden files in the Finder with the keyboard shortcut Command-Shift-.

For additional help, see Filters.