4% is nothing when it comes to estimation and it's close enough for us to be able to talk about it with reasonable certainty and validity. In terms of pre-orders, that would mean a figure of 300,000 is only off by 12,000, not 150,000. I have no idea if that is a typical variance or not, but in that one example it's peanuts. If VChartz' typical variance is 4% it's well worth discussing their figures IMO. I don't think it has to be accurate to the unit for us to have a conversation about it.