In its annual 10-K report to the US Securities and Exchange Commission (SEC), Microsoft has - for the first time - reported its actual revenue figures linked to the sales of its Windows 8-based Surface tablet in fiscal 2013 which ended June 30.

The lackluster Surface sales figures published in the Tuesday report reveal that, for the entire fiscal 2013, the revenue which Microsoft generated from the sales of its tablet was approximately $853 million --- a figure which is nearly $50 million lower than the $900 million charge which Microsoft took when it announced a $150 per unit discount for its remaining Surface RT inventory.

What is even more disquieting is the fact that while the $900 million writedown pertained only to the Surface RT tablet, the reported revenue of $853 million included the combined sales of Surface RT and Surface Pro tablets.

On the basis of the reported figures, it is quite evident that Microsoft has apparently failed to cover its costs for the Surface launch, with included a massive marketing push the company gave to its ill-fated tablets.

Against the backdrop of Microsoft's gloomy tablet-revenue figures, CEO Steve Ballmer recently confessed - at a recent "rally the troops" event at the company's campus - that Microsoft had "built a few more devices than we could sell," and added: "We're not selling as many Windows devices as we want to."