https://thenextweb.com/microsoft/2019/01/09/psa-windows-10-will-soon-reserve-7gb-of-your-system-drive-for-updates/

Fair warning: next time Microsoft rolls out one of its big semi-annual Windows 10 updates, you’ll probably lose a big chunk of storage. In a blog post, Microsoft announced that “with the next major update,” Windows will set aside about 7GB of disk space for updates, apps, temporary files, and system caches.

Though that may be annoying for those of us on limited drive space, the logic seems pretty sound. By Windows reserving space beforehand, you can avoid having to clear up space for updates later – something I expect is a big reason some people don’t install updates in the first place. It should also help avoid painful situations like when the October 2018 update caused user’s files to go missing.