The confirmation dialog, which is displayed by default, shows all the changes that will be applied during a sync grouped by files to be removed (left tab), overwritten (center tab) and added (right tab).
To skip the confirmation dialog and apply the sync changes automatically, enable the option “Skip confirmation dialog” in the sync settings Advanced tab.
By default, while the name of regular files is displayed in black, names of directories can be grey: in the Remove tab, grey directory names won’t be deleted (but contents with a black name will) and grey directory names in the Overwrite or Add tab will not be created because they already exist.
The modification date of directories whose contents have changed is also synchronised according to the overwrite policy. An optional dot “•” in the Size column indicates that only the modification date of a directory is going to be synchronised (and no contents are added or removed).
If the option “Always synchronise tags” in the Destination tab of the sync settings is enabled, files whose tags will be copied appear in grey and show a dot “•” in the Size column to indicate that the actual file will not be transferred.