Ah, I missed that link in your post aedon, sorry
The result for 10/30 doesn't count towards the first week (10/30 is Monday and the Oricon week ends on Sunday). But the weekly rank is more affected by the higher sales on the day of release in the beginning of the week than what happens later.
Koharu is really is the miracle girl. If you look at the first week sales, Kusumi Koharu does better than Abe Natsumi, Goto Maki and GAM lately. Ranking wise she loses to those three. So the weekly rankings mainly say something about how the single compares to other singles that week. If it is a slow week, there's a much better chance to get a high ranking with moderate sales. Although a high ranking is nice, that's not the only factor determining a single's succes IMHO.