Herman expected Tang Shaoyang to choose the Hell Difficulty. That was why he proposed first for Advance Difficulty so they could meet in the middle. He was not going to take the risk by choosing the highest difficulty. There might be a chance that they would meet a God Rank in the Hell difficulty.
"That's too risky for us, Sir Tang Shaoyang. Let's do it at Advanced Difficulty."
Tang Shaoyang just shrugged at him, "Up to you, this is your dungeon. However, this might be the only chance for you to try the Hell difficulty with me. As for me, I can try the Hell Difficulty with The Africa Nation. The Demi-God Dungeon spawned in their territory, and they requested assistance from us as well."