How can I remove duplicated items in the install updates list?
Something, somewhere, didn't register correctly.

Possibly someone maybe able to figure out exactly which receipt or App Store file to find, however, it would be far simpler &amp; possibly safer to just get the standalone OS X Yosemite 10.10.3 Combo Updater &amp; run it again; because you don't know what else didn't happen as planned either &amp; the Combo will make sure everything since 10.10.0 is correctly updated.

You can use a download manager to fetch it, too &amp; it will then be resumable if the download halts for any reason.
- examples at Download Manager for Mac OS X [though Speed Download, arguably the best, is discontinued.]