You should visit the "computers needing this update: 41" link you show in your screenshot. Yes, it's a LINK, even though it's not underlined. Then visit the report to see what systems claim they need that update. it's possible that the client system you have in the 1 target group that this update is approved to is NOT in NEED of this update.
Better yet, go to the computer report of the system that you want to upgrade, and click on the link for the needed updates. Then see what is not approved vs what is approved.