"from national retailers in each of the countries"
You have direct contact with these people and they provide you their sales reports ?
" a mix of Media Create, Famitsu, and our own data, weighted to roughly a 3:2:1 ratio"
So it means that every quantities we see here are calculated estimations ? no exact numbers of items ? (this is not a critic !)
For example the quantity of Switch at 176.591 units sold for June 30th might be a value to consider with +/- 3000 maybe ?