What is a single shard in a single shard?

Tree-ear, the main character, is on a trip to Songdo to show Emissary Kim the pottery made by Min. While he is on his journey, two robbers try to rob him at the Rock of the Falling Flowers. When they realize he has no rice, they throw the vases off the rock and they smash. Tree-ear then gets the largest shard from the broken vases and brings the SINGLE SHARD to Emissary Kim.