I really do not understand your question, I must admit. Are you talking about the basis for the sale? Or are you talking about the basis for the stock received? And, where are you seeing what you're reporting?
The way this deal was structured, your "proceeds" for the sale is the sum of the cash received plus the "fair market value" of the stock received. To calculate your gain or loss you simply subtract your basis in SNI from the "proceeds".
Your basis in the DIS stock you received is the same as the "fair market value" assigned to the stock. Your holding period for the stock starts the day after the deal closed. It's "as if" you received all cash for your SNI stock and then decided to take a portion of it and invest it in DIS.
Tom Young