The Surface Pro 4 has been out for a while, and its predecessor, the Surface Pro 3, has been more or less left in the sidelines. This is much to the distress of people who are still using the SP3, considering the device has been suffering from some battery life issues recently. Thankfully, Microsoft has released the first firmware release for the SP3 since August - one that hopes to fix those battery issues and put the Surface back in working order.
v126.96.36.199 corrects an error that may occur on a limited number of Surface Pro 3 devices where the full charge capacity of the battery is misreported to the operating system and device firmware. This update corrects the firmware component that functions as a "fuel gauge" so that the battery capacity is accurately reported. See Surface Pro 3 Battery FAQ for more information.
The update came out a few days ago - November 7th, to be exact. The issue was only really a problem for a select few devices, but it was still an inconvenience that needed to be dealt with.
It's probably going to be a while before the Surface Pro 3 gets any more in the way of firmware updates, considering Microsoft has moved on to other hardware quite a while ago. If more serious issues do come up, however, take this firmware as reassurance that Microsoft is dedicated to keeping the SP3 experience functional.