A bet resettlement is when the settlement status of your bet (win, loss, void) is modified due to previously being settled incorrectly. This can result in either a debiting of, or crediting to your account. Below are some examples of potential resettlement situations:
DraftKings reserves the right to adjust a payout credited to your balance if the payout has been credited to the account due to an error.
You can find more information regarding bet resettlements under section 6.1 in DraftKings General Betting Rules.