
Alissa G. answered 04/02/19
English & Spanish Language Lover-Grammar Geek-Word Nerd
Hi! I love seeing an excerpt from Harry Potter :-). Let me rephrase the sentence for you in the way that I am interpreting it, and then explain my thoughts:
The other two agreed with Harry, which showed how bad the last week had been.
Does my rewrite make it make a little more sense? I think the "mark" is just a synonym for proof or evidence. In other words, as the next sentence in your excerpt describes, the characters are all extremely eager to get rid of Norbert and Malfoy, so this is why they are so quick to agree to Charlie's proposal in his letter. I guess that if the last week hadn't been so bad, they might not normally agree to this type of thing. But precisely because it was so bad, they agreed, which was proof that it had been a bad week.
Hope this helps!
Kind regards,
Alissa G.