When you search a document on Quetext, your text is first split into sentences. When a sentence is wrapped in quotation marks, it will be interpreted as a cited text, and thus will not be considered as potential plagiarism.
Partially quoted sentences
Sentences that aren't entirely quoted, are considered for plagiarism search if the quoted portion of the text is 50% or more of the entire sentence. For example, consider the following sentence:
By early 237 BC, "after multiple setbacks, the rebels were defeated and their cities brought back under Carthaginian rule".
Note that in the above example, the entire sentences isn't quoted; however, more than 50% of the sentence is quoted, so the entire sentence would not be considered as plagiarism.