Mark, If you have decided who you are is an honest man do not add any lying to the issue.

If I think back I have done the same thing more than once; and I kept the money. Because I am not that guy any longer I would simply tell her you made an error and would apply a $50 credit to your next job. This way you may ensure another job and you have been honest. (She will remember you as an honest man)

IMHO, John C.

PS, You gotta love that Donny he gets to the legal part right away. Mr. Business. Not a bad thing.