...and if it actually is the Windows 10 April 2018 update, then it IS a large download and will take quite a while to install while online. Some are experiencing 2 hours + for download and installation, depending on your download speed.
To be sure that it is the Windows 10 2018 Update, after it installs and restarts your computer multiple times, you can check the version number by typing "winver" in the lower left search window. The version number immediately after install should be "version 1803", and the build number should be 17134.1.... or possibly 17134.228 if all the most recent updates are now included in the install.
Hope this helps.
Grif