While we've had problems with 2 [out of a dozen] Windows 10 Anniversary Upgrades, plenty of folks haven't been so lucky -- allegedly it will be November before Microsoft has things fixed enough to push out the upgrade to any remaining Windows 10 devices. In the meantime those cumulative updates keep rolling in, filled not just with security patches but bug fixes. And this last one was large...
Running Disk Cleanup from the Windows partition's properties dialog in Windows Explorer, click the button to show [clean] system files, and you should see an option to cleanup leftover Windows Update files. While the 32 bit copy of 10 only showed just short of 900MB that would be deleted, all the 64 bit versions showed 1.3GB+.
Now Warning... it can take an awful long time to clean up those update files -- over an hour on low powered devices. It's also not really multi-threaded, so while it doesn't take 100% CPU, it will max out one or two cores, getting almost as hot & using almost as much power.