The Squirrly Snippet shows you how your article will look on search engines. By customizing it, you will boost the conversion rate.
By default, Squirrly Snippet generates the meta-information for your article. When it creates your meta description, it basically takes the first lines of your article and it integrates them.
It also checks if your keyword already appears in that text section. The wrong thing to do for an automatic SEO software would be to not give you the possibility to customize your text, and to take the same one that is used for the main site for each page, therefore generating duplicates.