The three words for the day are:
plausible, taint, willingly
My submission is as follows:
It is just not plausible that I would make such a big error. But reather than tainting the opinion of the auditors, I willingly provide all the documentation I can find.
Let the auditors determine who is responsible for the error. If I am ultimately responsible, I can accept their decision and endeavor to not make the same type of error again.