"M" to "F" in birth certificate

A client consulted me about her daughter's birth certificate.
The client said that instead of the letter "F" for "female" on the "sex" portion in the birth certificate, the letter "M" was erroneously typed.
I told the client in jest that perhaps the mistake was done by the nurse in the hospital who wrote the wrong "sex" of the new born.
Perhaps the nurse mistakenly saw something protruding in your daughter's private part when she was born.
That might explain the mistake, I quipped.
The mother vehemntly denied this suggestion and said this might just have been simple a typographical error.
I told the client that an interchange of the letters "F" and "M" on the sex portion of the birth certificate is not considered a typographical error.
It is a substantial error that requires one to bring the matter to court, in order that it may be changed.
It is akin to a man who undergoes a sex change and wants to change the letter "M" to "F" in the birth certificate.
That is a substantial change in the birth cetificte because it changes the person's gender.
A substantial change requires a court proceeding.
The mother was a little naughty because she asked a hypothetical question:
What if the wrong letter typed in the birth certificate is, for instance, the letter "N"?
Will that not be a typographical error, considering it is neither "M" (for male) not "F" (for female)?
I said it is still a susbtantial (not mere typographical) mistake because "N" might mean "None of the above".