How many articles do i get from a spun article ?

There is one thing i never understood since i have never used software or so.
How many different versions of articles can i get out of a spun article ?
And if i put the article somwhere on senuke, where it creates 1000 properties with articles, how do i know about the uniqueness of the articles, i mean how do i know, that it does not leave footprints at the end ?