In J.R.R. Tolkien's The Hobbit, what did Thorin promise Bard in exchange for the Arkenstone?

In J.R.R. Tolkien's The Hobbit, Thorin grudgingly promises to give Bard a "one fourteenth share of the hoard in silver and gold" (262)—Bilbo's original allotment of treasure—in exchange for the precious Arkenstone, the Heart of the Mountain. Bard acquired the Arkenstone through covert means, as Bilbo secreted it away from the Lonely Mountain in the dead of night and gave it to the lake men. He originally did so not out of spite for the dwarves, but to force Thorin to share some of the treasure with the beleaguered citizens of Lake Town, as Thorin could not bear to be parted from the beloved gem. By doing so, Bilbo hoped to avoid a likely war, but, unfortunately for the well-meaning hobbit, a battle erupts anyway when the loathsome goblins arrive and force the dwarves, men, and elves to unite against them. This scene, in which an incensed Thorin condemns Bilbo and even threatens to kill him, is a poignant and frightening illustration of greed, as former friends are turned against one another in a bitter quarrel over money.