Mac OS X Server 1.x does not include the resource fork in the size reported. Only the data fork size is reported. Workspace has the ability to copy both forks of a file so they can be moved and copied correctly between Mac OS or Mac OS Extended volumes.
To correctly determine the file and folder sizes on Mac OS or Mac OS Extended volumes, either use MacOS.app or mount the volume on an AppleShare client (only Mac OS Extended volumes can be shared), then use the Finder's Get Info command.