how VSR18 offsite copy works

How does VSR18's offsite copy work? From what I understand, we just file copy the backup image file that was taken to another location (whether it be a file share on-premise or to the cloud) correct? We don't do anything special with offsite copy do we? (ex. compress like we do when creating backup images). Customer is concerned about the size of the offsite copy which they want to store to cloud and they're asking if we do anything special to reduce traffic on the offsite copy.