https://www.theregister.co.uk/2019/01/10/new_windows_10_build/

Microsoft dropped a fresh Windows 10 Insider Build last night, which brought some welcome tweaks to the Windows Subsystem for Linux and enabled Reserved Storage.

We had been promised that the exciting new feature in build 18312 would snaffle around 7GB of space but, as it transpired, we at Vulture Central have not been blessed by the Windows Update Gods, and only 2.83GB vanished from our system drive.