The difference between 93 and 90 is 3.3 percent, and the difference between 7.6 and 6.7 is 13.4 percent. It seems impossible to make the same error for both. Also, this is an estimate and we can't expect the numbers to match exactly.
I don't think taking the totals and looking at the estimation is the best way to go about this. Seeing as we know Nintendo's shipment numbers for fact, it'd probably be better to go off of the sales data for this fiscal year. It's not like Ampere and VGChartz have gone all the way to 93M and 90M without adjustments based on Nintendo's shipment information.