I believe you have some missunderstanding about stand development in Rodinal. It is NOT the dilution rate, but the ratio between the volume of developer to film area. If you used 5ml Rodinal to 500 ml water you have pushed the film by one stop. The box speed ratio is 3.5ml Rodinal in whatever volume of water you use to cover the film, 500ml, 1000ml,.... . Two rolls require 7ml Rodinal.