Given that KB2999226 is for updating the Universal CRT (C RunTime) in Windows...
The Windows 10 Universal CRT is a Windows operating system component that enables CRT functionality on the Windows operating system. This update allows Windows desktop applications that depend on the Windows 10 Universal CRT release to run on earlier Windows operating systems.
Microsoft Visual Studio 2015 creates a dependency on the Universal CRT when applications are built by using the Windows 10 Software Development Kit (SDK). You can install this update on earlier Windows operating systems to enable these applications to run correctly.
I would presume that having all the Visual C++ redists and VS2013 installed etc has probably installed this update for you. Given the choice of installing several gigs worth of VS and redists... and installing a simple update, I know which route most users would take