Sealed moves in title matches

Hi, since the next title match with a two-day game is starting soon I have a question regarding the sealed move. How is this decided? Is there a certain time of day a player can declare that they are sealing a move? Is there a minimum amount of moves played that must be made beforehand, or a certain amount of time gone?

Also, are there any statistics on win-loss rate regarding sealing the move or not?

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