If this girl can't spin five skeins, she will be killed by king.
However, all of a sudden she heard a sort of a knocking low down on the door. She upped and oped it, and what should she see but a small little black thing with a long tail. That looked up at her right curious, and that said:
'What are you a-crying for?'
'What's that to you?' says she.
'Never you mind,' that said, 'but tell me what you're a-crying for.'
'That won't do me no good if I do,' says she.
'You don't know that,' that said, and twirled that's tail round.
'Well,' says she, 'that won't do no harm, if that don't do no good,' and she upped and told about the pies, and the skeins, and everything.
This content is from "Tom Tit Tot" in English fairy tales.
I can't understand these sentence "That won't do me no good if I do","You don't know that", "that won't do no harm, if that don't do no good". Is "that" a small little black thing?