This article discusses the behavior of SureSync and SureSync MFT when adding a new path to an existing Job that has already been run.
When adding a new path to an existing Job, SureSync simply copies the files to that path, resulting in the same synchronized content as the other paths. Deletes are not enabled until file history exists for a path.
You can pre-populate the data set if you like. For example, using a copy of the data on a USB hard drive. This can make sense when there is a large amount of data that has to be transferred. If you take this approach, the Job will resolve any differences when the Job is run for the first time, so they all match. If a file has been updated since the time the USB hard drive copy was generated, it will be copied to the new path. If a file has been added since the time the USB hard drive copy was generated, it will be added