That’s indeed what he was saying. If there’s any actual concept of Justice on a cosmic level, then “eternity” is certainly not a “just” punishment for anything done by a mortal, subject to circumstances and born into a world they had no choice in. In a “just” universe with a punitive afterlife, Hitler would get back an equivalent amount of suffering to that which he caused. So maybe a few hundred million years worth of suffering, but not eternity.