Okay how did you upgrade to macOS Sierra.
Did you visit this page
How to upgrade to macOS Sierra - Apple Support
Did you download InstallOS.dmg to your Downloads folder.
Did you open it to InstallOS.pkg
Did you open that and get an installation window.
Did it say it would take 13.5MBs of disk space.
Did you know that does not install macOS Sierra
Did you know it creates the Install macOS Sierra.app in your Applications folder.
Did you look in your Applications folder.
Double-clicking on Install macOS Sierra.app will launch the OS installation screen.
Did you know that on completion of the install the Install macOS Sierra.app self deletes.
Did you know you should copy the Install macOS Sierra.app to an external drive
in case you need to reinstall Sierra or install it on another mac.