Q: If an update has been downloaded more than once, what can I do?

What version of OS are you using - your profile shows 10.1?

Try re-indexing Spotlight. The App Store uses it to determine what is installed.

Spotlight – Re-index

Hide Updates  This doesn't work on updates to Apple applications.

Software Update – Stop it From bugging you

Try resetting the App Store and Clearing Cookies.

Reset       Learned from Old Toad

App Store support. There is troubleshooting and a contact link.

Support