Delete the small installer from your Applications folder and empty the Trash.
Replace "MyUSB" with your USB drive's name. Macos High Sierra 10.13.6 Raw Download
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --nointeraction Delete the small installer from your Applications folder
For those without access to a Mac who need a raw file to flash to a USB drive on Windows, Olarila is a popular community resource. : They provide Macos High Sierra 10.13.6 Raw Download
http://updates-http.cdn-apple.com/2019/cert/061-39476-20191023-48f365f4-92b5-4f8e-9a89-3d7b3b14ebef/InstallMacOSHighSierra.pkg