how does this affect a credit score vs Settled In full for less than the amount owed

Bo, how does this affect a credit score vs Settled In full for less than the amount owed.
My wife's score is a 778,and we are short selling our home. We are closing with only one late payment on her credit.
What do you think????
Have you ever heard of a bank taking this off after the fact for a little extra money????
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maybe
IF
you have never had a late payment and they reach a settlement then there may be NO after effect but, i am not sue and cannot advise 778 is for all practical matters a perfect credit score if you were never late and get a settlement i would think you could go no lower than 680 which is still a good score but one can never tell for sure as scoring algorithms changes all the time