Okay here are a few usage examples to help make the different features more apparent. (This assumes you have already enabled Inline Posts) All options described blow can be found on the "Posts & Pages" tab.
Recreating WordPress default behavior.
Following these instructions will only split a post on a tag, as WordPress does by default.
Select the option to create excerpts "Only on more or nextpage tags."
Change the Show and Hide texts to whatever you like.
Recreating WordPress default excerpt behavior.
Following these instructions will duplicate the normal WordPress excerpt.
Select the option to create excerpts "By word count (exact word count)."
Right below these options, in the textbox set it to 55 to split the excerpt to exactly 55 words.
You can also select the option to "Strip HTML in preview" like WordPress does normally for excerpts.
Other variations include using full sentences instead of an exact word count or splitting by paragraphs instead of words.