It seems that the documentation is not clear enough. Please file a bug in trac.
Share path:
A path can be created either in the eBox directory /home/samba/shares or using an already existing directory path if File system path is chosen.
It should say:
If you pick
File System Path you will need to create the directory manually if it doesn't exist and set the proper permissions in order to be accessed by your user. However, if you pick
eBox, the share will be created automatically along with the right permissions under
/home/samba/.
Help us make a better product by reporting this kind of stuff. If the doc it's not clear let us know.
As far as I know the 2.0 doc is not ready yet, but you can use the 1.4 doc which I suppose will be very similar:
http://doc.zentyal.org/en/filesharing.html#file-sharing