While reading "Harry Potter and the Philosopher's Stone", I came across the next line, said by Hermione Granger:

> 
> 'If they hadn't found me, I'd be dead now. <..>
> 
> 
> 

But, according to the rules, the sentense should have been like:

> 
> If they hadn't found me, I would've been dead by now.
> 
> 
> 

Am I wrong?
What is the difference between these two sentences?