Good catch. My apologies. I checked the original article cited and unfortunately there is simply no way to determine just what the storage breakdown is from the information provided since there are no figures given for 64GB wifi, 16GB 3G, or any breakdown for the 32GB models. I'd dig further but since the article is based on a survey of Western Europe soon after introduction of the iPad 2, I'm not sure what it would tell us.
BTW, in a previous life I made a living doing market research and will only say that without access to the raw data upon which articles like this are based, it's almost impossible to figure out what's going on. And even then the conclusions are frequently heavily qualified. For example, market research firms like Context (in Western Europe) and NPD (in the US) get much of their information from retail channels with whom they have agreements to supply sales figures. Unfortunately for any reasonable analysis, Apple refuses to divulge just how many (and which) iPads they sell through their own retail stores (or via the internet) though such information is available from resellers. Thus, although the actual sales of Android tablets (for example) can be relatively accurately estimated by checking with a sample of retail outlets and internet sites (because they are the major channels), the same is not true for iPad sales. The only way around these problems is to survey consumers directly. But that sort of research is far more expensive than monitoring retail channels and isn't conducted very often.
There's no question, of course, that Apple dominates the tablet market at the present time. But apart from Apple's own press releases, there is almost no reliable source of just how extensive that domination is. The same, by the way, is true of the Kindle Fire from Amazon. There is little question that it is selling very, very well. And in some retail channels where both the Kindle Fire and iPad are both available (e.g. Best Buy, Target), the KF appears to be a strong competitor. But since Amazon, like Apple, doesn't release figures about its own direct sales and those sales constitute a large portion of all sales, it's very difficult to derive precise estimates of total sales for either the iPad or the KF.
Sorry for the tangent.