As a general rule, making a gift is an intentional act. You can't make a gift by mistake. I assume the extra money has returned to you. Since you had no intent to make a gift in excess of $140,000, and the excess contribution has been removed from the account, your gift to the 529 account for 2016 is $140,000, and that is the amount you should report on Form 709.
I assume that your gift to the account meets all the requirements for "superfunding" a 529 account. Please see page 6 of the instructions for Form 709 for more information.
https://www.irs.gov/pub/irs-pdf/i709.pdf
