Content of Teaser Field inserted into Body field

I enabled the module, created a field_teaser CCK field for my Story content type.

Under Content Management >> Content Teasers I find my new field_teaser and set it to "Teaser Field" and "Synchronize". I assume that "Synchronize" grabs the default first 600 characters from the Node Body and inserts it into the field_teaser field, but I believe my assumption is wrong. I have no idea what "Synchronize" does.

I have a story-node template pointing to $node->teaser to get teaser value for a node. I edit a Story node and type in a dummy teaser. I go to the view of my template and there is my dummy teaser text. Yay!

BUT, I go back into the Edit screen for my Node. The teaser text has been inserted into the head of the story body. ACK! That's not what I want.

I want the teaser field, if filled in, to be what is returned when requesting $node->teaser text. If it is not filled in, I want the $node-teaser to return the Drupal default teaser (first 600 characters of the body, which I can adjust in the admin settings). But i want them separate fro one another.

Is that possible? Does the content of the custom teaser field (called 'field_teaser' in my case) HAVE to be inserted into the body field for me to be able to have the conditions I described above?

Also weird, even though the Body text now has field_teaser's text in it, it doesn't show up in the Node's view with the rest of the story body. But it's confusing to the editors (newsroom editors are rarely tech-savvy - inserting non-story-body text into the story body will confuse the hell out of them)

as for documentation, the real issues are A) what does "Synchronize" actually do? and B) "Construct teaser only from teaser fields" in a content type's Edit >> Workflow settings, does that mean, when enabled, that the body field NEVER gets used for teaser?

Thanks! Much appreciated.