Oricon Ninki rankings do not reflect the amount of sales or placement of a single/album. It's actually just a poll conducted upon Oricon subscribers about popularity.. I think.
Like, 4Minute got ~22 on the Ninki rankings and only sold like 4.5k copies. (I remember because of all the arama trolls back then) But sometimes groups like Arashi who score like 400-500 Ninki points sell way over 500k copies. We'll wait and see [and pray]. :]