Re: Terrible maths.
Firstly, the article clearly said it was "the lion's share of the Hardware division's $1.9bn revenue HIKE..." You left off the crucial word "hike", thus misrepresenting what the author was saying, namely that the 54% gain in XBox revenue in the past year outweighs the total current revenue from Surface.
According to Microsoft's own press release, your interpretation that Surface revenue "now accounts for nearly half of the Hardware division's revenues" is simply not true. Microsoft says that "Surface revenue more than doubled sequentially, from $400 million in the first quarter to $893 million in the second quarter." (http://www.microsoft.com/investor/EarningsAndFinancials/Earnings/PressReleaseAndWebcast/FY14/Q2/default.aspx)
Since the Devices & Consumer Hardware division's latest quarterly revenues are $4.73 billion as the article correctly reported from Microsoft press release, Surface's total of $893 million only accounts for 19% of the division's TOTAL revenue, as opposed to 47% of its year on year INCREASE in revenue.
So there was no bad maths involved, at least not on the author's part. On the contrary his figures fully substantiate his statement that "you can't credit [Surface sales] for most of those gains."