From "Not like this" by Jane Walsh:
"I was the third of six children, four girls and two boys. We lived in a Lancashire cotton town - and when you add that we lived in that town's slummiest and dirtiest quarter you are saying something!"
I don't fully get the "you are saying something" part of the sentence (though I feel the meaning). Could you help me with this?
you are saying something = it was extremely slummy and dirty- the whole town would be pretty bad, but her area was unbelievably so..