In "To Kill A Mockingbird", Scout said "He ain't company, Cal, he's just a Cunningham." What does she mean by this statement and what was Cal's response?

Scout means that since Walter is poor he shouldn't be treated as a "normal" guest would because he is, in her eyes, worth less in a way. Cal takes Scout to the kitchen and scolds her, pretty much saying he's your guest and you better treat him with respect. She gives Scout a little spanking too and sends her back to apologize.