Is it a one off error? Has it happened before?
If one off, then s it really such a bog issue? Chances are it was a human error when rushing to mark all 30 odd books for literacy. Why the need to make the teacher feel embarrassed about it?
If not a one off then fair enough, go and speak to the teacher.
I wouldn't write in the book personally. I'd rather deal with these things face to face as adults.
Everyone makes simple mistakes sometimes, especially when busy.