Q: App store telling me to upgrade to 10.11.6

How should we know. Your profile shows you are using 10.11.2, not 10.11.6. You may wish to read Writing an effective Apple Support Communities question.

The one from the Apple Forums below your original question post. The update you see would be the Security update, then. You have the download link from my previous post. If you see a badge on the App Store's Dock icon, then open App Store, click on the Updates icon. Wait until the spinning gear stops. The update should then appear at the top of the window.

That security update was released yesterday, not on July 24th.

Maybe they said (or meant) security update for 10.11.6?

Security Update 2016-001 El Capitan and Security Update 2016-005 Yosemite

There were two just released. One for El Capitan and one for Yosemite.

If you are showing the 10.11.6 update and not the security update, try re-indexing Spotlight.

Rebuild the Spotlight index on your Mac - Apple Support