"Sit down, dear, I'll knock something up."
As Harry sat down a furry ginger cat with a squashed face jumped on to his knees and settled there, purring.
"So Hermione's here?" he asked happily as he tickled Crookshanks behind the ear.
Oh yes, she arrived the day before yesterday," said Mrs Weasley, rapping a large iron pot with her wand it bounced on to the stove with a loud clang and began to bubble at once. "Everyone's in bed, of course, we didn't expect you for hours. Here you are -"
Harry Potter and the Half-Blood Prince
I don't quite understand "we didn't expect you for hours" in this context. Maybe, the use of "for hours" confused me. What does it exactly mean?