1) No, don't use $0 cost, that doesn't help. Use your actual cost.
2) What was the total value of the donation vs. your AGI? If it was over 30% of your AGI, then the donation that can be used this year is limited to that 30% of AGI value, and the excess is carried over to be used next year. And if it is limited due to the 30% limit, and you haven't entered all your income yet, then the amount used will change as you add more income.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
