They had wandered away from the cone king without any clue as to where to find the rocks (tiny rocks) when Finn tripped and fell. As he looked at what he was lying on, he noticed that the ground was covered in little round-ish hard things. He asked Leon what they were and Leon quickly stated that what he was lying on was gravel.
Finn asked if gravel was the same thing as rocks (tiny rocks), Leon assured Finn that gravel and rocks (tiny rocks) were not at all the same thing. Finn wasn’t so sure.
While Finn was listening to Leon pontificate on why gravel and rocks (tiny rocks) are not the same thing, a passerby overheard them and stated that yes, they were the same thing!
“Oh, good”, said Finn. Leon just stopped talking.