Ballmer and Co. have been tight lipped when it comes to Surface sales figures, but they've just opened up a little to Uncle Sam. An SEC filing reveals that the first-party tablet raked in a total of $853 million in revenue between its debut and June 30th, the end of the firm's fiscal year. To put that in perspective, the cash Microsoft managed to pull in is eclipsed by a $900 million hit it took through Surface RT inventory adjustments. To make matters worse, the company spent more on advertising for Windows 8 and Surface ($898 million), than its tablet brought in. Though details on how many slates have shipped or sold are still MIA, price drops make us suspect that those numbers are still too modest for Redmond's taste.