Hi Bulan,
"~ 기만 해봐(?)" = a format used when threatening or warning someone.
If I translate this, it would sound like "Let's see what will happen when you do ~" or "you'd better not to do ~".
Some people put question mark after it but they are not really questioning. Maybe just to sound sarcastic.
Ex1.
아들: 엄마, 저 오늘 그냥 집에 있으면 안돼요?
(Son: Mom, can I just stay home today?)
엄마: 너 오늘도 학교 안가기만 해봐. 아빠한테 말할거야.
(Mom: Let's see what will happen when you don't go to school today as well. I'm going to tell your father)
Ex2.
민지: 정말 미안해. 다시는 안 그럴게.
(Minji: I'm really sorry. I won't do that ever again)
민호: 알았어. 대신 또 그러기만 해봐. 또 그러면 너 이제 안볼거야.
(Minho: Fine. But you'd better not to do that again. If you do again, I'm not going to see you anymore)
Ex3.
수지: 언니! 오늘 말도없이 내 신발 신고갔지? 또 그러기만 해봐.
(Suji: Sister! Did you wear my shoes without telling me today? You'd better not to do it again.
언니: 또 그럼 어쩔건데?
(Sis: What's going to happen if I do it again?)
Ex4.
민지: 여기 고기 들어있네. 나는 안먹을래.
(Minji: There's a meat in it. I'm not going to eat it)
민호: 그거 감자야. 그냥 한번 먹어봐.
(Minho: That's a potato. Just try it)
민지: 고기 이기만 해봐?
(Minji: It'd better not to be a meat? (trying to sound like 'Minho you will be in trouble if it is meat!))
So, back to your sentence...
"오타 이기만 해봐?!" = It'd better not to be a typo?! (you will get in trouble if it was a typo)
Hope this helps,