Bold: that's already enough to know what you mean. No real number or proof, all are meaningless.
The irony is that this very site is just one big assumption as well with no "real" number or proof unless taken from official sources, hence the constant adjustments month after month, quarter after quarter when real or more reliable data comes in.
Based on all the adjustments in the last quarter, drkohler's estimate is entirely possible and is in no way better or worse than VGChartz estimates. There have been times when they even made adjustments in the multimillions. Either way, we will all find out in about a months time when Sony announces their quarterly numbers.