Does FTP Synchronizer synchronize changed files only?

Yes! Thanks to the powerful tracking technology, FTP Synchronizer can detect file changes and synchronize these files only. Unlike other programs which synchronize all files every time, if no files were changed since the last sync, FTP Synchronizer will skip these files automatically. It will save a lot of bandwidth, and more importantly, your precious time!

This is first time I use FTP Synchronizer, I already have same files in local computer and FTP server, why did FTP Synchronizer want to synchronize all of them?