In  a novel method was established to estimate the minimum distance of primary affine variety codes and a thorough treatment of the Klein quartic led to the discovery of a family of primary codes with good parameters, the duals of which were originally treated in [Ex. 3.2, Ex. 4.1]. In the present work we translate the method from  into a method for also dealing with dual codes and we demonstrate that for the considered family of dual affine variety codes from the Klein quartic our method produces much more accurate information than what was found in . Combining then our knowledge on both primary and dual codes we determine asymmetric quantum codes with desirable parameters.