[Plugin: Smart DoFollow] What does Range Options mean?

I don’t know what does range options mean.
I am a user from Chinese.
I have install this plugin correctly. I have set Minimum number of chars to 30.
I have a page like : 关键词选择应该注意什么？, and there is a review, when I look at the page source code , the The author’s signature have nofollow attribute, and the links in comment content have no nofollow attribut, is this correct?
What does the range options exactly mean ?

http://wordpress.org/extend/plugins/smart-dofollow/