The Bible often uses a figure of speech called litotes. Litotes is simply a negative statement used to express an affirmation, as in "He is not a bad preacher" (meaning that he is a very good preacher). Don't miss this when reading your Bible. One example will suffice. In Acts 21:39, Paul says that he is "a citizen of no insignificant city." He meant that Tarsus was indeed a very significant city. See also Acts 12:18 and 27:30.
Don't ignore a litotes!