That's the latest feature update - that tries to reserve 9GB of HD space for future updates!
So will never install on a 32Gb eMMC machine where Win10 already uses more than 20Gb of the 28 or so Gb of actual usable space.
I have moved everything possible to a USB stick (update folder, filesystem, etc)....no joy.
Why do you write an update that even when the update cache is on a different disk insists on still trying to reserve it on C:?????