Says a thing is only right when done a particular way: 그렇게 해야 맞아요 'that's how it should be done', 이건 치즈 앤 맥이라고 해야 맞을 듯 'it should really be called cheese and mac'. It is about correctness — the right word, the right way to serve something — not about obligation, which -아/어야 되다 would carry. Note that 맞다 has other senses too, and two lines here use them instead, one about getting an answer right and one about being struck.