Snap servers and permissions - why is there no write pwemission for folders, etc.

I'm trying to set up a Snap server 2200 on an NT domain.  It sees all the NT users OK.  I want to set up permissions to limit access to files and folders and can't get it right.

First, I am trying to keep people from deleting anything - shouldn't be able to delete folders, shoulnd't be able to delete files.  They should be able to create, open, edit, copy (but I guess not move, since that would involve a delete?) any file or folder.

I have network shares set to everyone - full access.

FOr folder / file   permissions, I only have  no access, read, add, read and add, change and full control.  The help pages talk of a write option, but I don't see it here.

It would seem that read and add or change would be what I want, but can't seem to get it working...