Socrates claimed that he knew nothing. He meant that his knowledge, compared to the knowledge of God, was nothing.
Still, “nothing” is as transcendent as “everything”. Neither word can be said except by a being who already knows all things. In saying “nothing” I negate all, which requires that I already understand the all.
Socrates’ statement is superlatively wise because he sees wisdom as knowledge relating to God. God is the cause, measure, object and fulfillment of all wisdom at least as Socrates’ understands it. God is the cause, because Socrates begins to seek out wisdom in response to an oracle of the god; God is the measure, for all human wisdom is reckoned as nothing in comparison to him; God is the object, because the goal of the philosophical life is likeness to God (Theatetus); and he is the fulfillment, for all things seek their fulfillment in the perfect, and all men desire wisdom.