My daughters last name....

Teja

So I discovered my daughters last name (her dad's last name) is incorrect /possibly misspelt. The story doesn't even make any sense to me, it's spelt wrong on her dad's birth certificate. When he pointed it out his mums response was "ohh". I think there's more to the story but it isn't my place to pry. It's just annoying cos everywhere we go people say "I've never heard of it being spelt this way, are you sure it isn't misspelt?" I just laugh it off and leave it at that. My partners dad isn't in the picture incase you're wondering. Anyway I know it's very unlikely but has this happened to anyone else??