Problem with Yahoo account?

I just set up an account for my daughter under my email, and as I was doing it, it asked for my credit card number to verify that I was of age...And to the right of the screen, it said "We will not charge your account." But, I looked at my online bank statement today, and I have a charge for $1....I know it's just a dollar, but dammit, they said they wouldn't charge it...Any one have a clue why they did, and what that was for??