Shakuni is considered being good at dice even though people say that he deceitfully won Indraprastha for Duryodhana. My question is, how is Shakuni so good at playing dice that whatever number he wants, it appears on the dice?
Shakuni actually used deceit; it wasn't only skill even though he referred to his deceit as skill.
"Hearing these words of Duryodhana, Sakuni replied,--'Hear how thou mayest obtain this unrivalled prosperity that thou beholdest in the son of Pandu, O thou that hast truth for thy prowess. O Bharata, I am an adept at dice, superior to all in the world. I can ascertain the success or otherwise of every throw, and when to stake and when not. I have special knowledge of the game. The Son of Kunti also is fond of dice playing though he possesseth little skill in it. Summoned to play or battle, he is sure to come forward, and I will defeat him repeatedly at every throw by practising deception. I promise to win all that wealth of his, and thou, O Duryodhana, shalt then enjoy the same.'"
Shakuni says that he is "an adept at dice" and that Yudhishthira possesses "little skill" in dice. He later calls his deceit as skill in the last bolded line.