Now how the heck did he know that? Did he read the Kryptonian Law Library before he was shipped off as an infant?
Silver Age Superman was able to fly back in time and observe or even visit Krypton. He also had the miniaturized, bottled Kryptonian capital city of Kandor, complete with its entire miniaturized population, stored in his Fortress of Solitude once he freed it from Brainiac.