Ryu shook his head.
The Heavens were giving him a choice. Either he could pick five treasures from any of the given God Treasures here, or he could receive a divination of fate that could be used to bring him toward exactly what he needed to perfect one thing.
Ryu assumed that this "one thing" was meant to be a limiter on what he could ask for. For example, he couldn't just ask to perfect his path of cultivation itself.
He actually didn't believe that the Heavens would stop him from asking such a thing of it. The problem was how much quality the response would have. Someone might jump at the chance, but Ryu, as a Ruin Master, understood better than anyone else what it truly meant.
"One thing", translated in this context, wasn't about quantity, necessarily, or at the very least, not directly. Rather, it was a hidden warning about the breadth of the requests Heaven would allow.
