What did Apollos learn about his own knowledge from Priscilla and Aquila, two tentmakers?

Les explains that Apollos was highly educated, polished, and eloquent in the Scriptures, yet when he learned from Priscilla and Aquila, two common tentmakers, he suddenly realized there was a lot he did not know. They had been with Paul and had received the tremendous gospel of grace—that everything man needed was accomplished on the cross and in the power of resurrection. Apollos knew none of that. Les points out that Apollos took it like a man, humbly acknowledging, in effect, that he had never seen this before. He took to heart what he learned from this Jewish couple. Later, when he was disposed to pass into Achaia, the brethren wrote exhorting the disciples to receive him, and he helped them much—not through John's message, but now through grace. He got it from Priscilla and Aquila, who got it from working with Paul.