Downloading El Capitan Disk Image is not the correct OS

I just downloaded the El Capitan disk image to upgrade a 2010 Macbook Pro running Yosemite. But I think it's mislabeled because I ran the installer and it didn't update the OS; it's still running 10.10.5. Where can I get the proper download?

EDIT: Sorry, I just discovered an older question asking this same thing. I did not realize the package installed the installer! I thought there was some other reason it was so small. Sorry for the duplicate, if I knew how to delete this I would.