Wading into the “muddied waters” of rounding the numbers used in a range claimed in two drug patents, the U.S. Court of Appeals for the Federal Circuit refused to set a “bright line rule.” Instead, it tossed a lower court win for Actelion Pharmaceuticals Ltd. against Mylan Pharmaceuticals Inc. and sent the case back to that court with instructions to consider the extrinsic evidence and its impact on the claim construction.