According to a fan, it seems that Oricon chart now does not support bulk (more than two copies) purchases!!
Other than the rule about Oricon counting locally-shipped purchases only, there seems to be a new one:
To make our purchases count, just buy only 2 copies for each bill. For example, if you purchases 10 copies or 5 copies on a single bill, this will be counted as 2 copies only on Oricon.
We aren’t sure when this rule has started. If it is exactly true as stated, we wish we knew about it before