Even if it is, the X1 will still catch up to it soon.

VG chartz is about spot on with the Wii U numbers, there wont be many sat on store shelves waiting to be sold, as retailers will only order the bare minimum.

Undertracked ? By VGchartz ?
I think it's fair to say : yes probably.

Maybe a little bit in Europe, but the numbers from the USA and Japan should be pretty reliable.

This. They FORECAST 6.25m SHIPPED end of March. In all likelyhood it probably hasn't even gone beyond 6m yet.

Actually statistically speaking the opposite is true.

It's much easier to get within 10% of something that sells 10 Million then it is something that sells 10,000.

With smaller samples it's a lot easier for one or two stores or chains to have a huge amount of sales that throw your numbers off, or have a huge drop off due to some sort of warehousing errors or just in general a huge pattern change.

Outliers matter more and you need a much tighter formula when sales numbers are low.

Now if you mean just rank numbers sure... it's more likely a higher selling console is going to be 500K off then a lower selling one.    However, it's far more likely for the lower selling console to be off if your talking a percentage of sales.

Well, assuming the higher selling console doesn't have any stock issues.  Then you've got all kinds of issues because you don't know who is getting preferential stock among retailers etc.

So, Wii U is more likely to be  under or over tracked copaired to say, the Xbone.

Of course it's worthing noting, under OR over.

Not just one.

Actually now i think about it, Wii U could be slightly undertracked in Europe. I remember around Christmas time that VG chartz had undertracked France by a considerable margin.

Im quite confident that it has crept past 6 million, i cant see many Wii U units sat on shelves waiting to be sold, as retailers will only be holding minimal stock.

If anything it's overtracked in Europe.

Well you shouldn't be, whatsoever. Nintendo very rarely even hit their forecasts, so less than 390k should be expected. LTD shipped should be 6.25m end of March or less. 250k or less in the channel WW is not a lot but about right for WiiU.

The OP basically expects more WiiU's sold than they have actually shipped.