The article below mentions that the directions of meridians at poles is 62 degrees. This value has been corrected. The new value is 63.883 degrees. This change was necessary due to a bug in early versions of Flex Projector, which has been fixed in a more recent version. The correction to the angle value was required to avoid any change to the graticule of the A4 projection when loading the parameters with newer versions of Flex Projector.

Article:
Jenny, B., Patterson, T. and Hurni L. (2008). Flex Projector—Interactive software for designing world map projections. Cartographic Perspectives, 59, p. 12–27.
Available at http://jenny.cartography.ch/pdf/2008_Jenny_etal_FlexProjector.pdf