It would be best for such to install in one go but this one does not. I recall this happened before. But won't research it.
Yesterday, I ran KB4494441 update here on two different computers and got the same results. After clicking on "Check for Updates" in "Settings-Updates and Security" and allowing things to proceed, detect the various updates, download, install and restart, both computers showed the update as installing successfully. But when I clicked on the "Check for Updates" button again, the cumulative update came up again, downloaded again, installed again, and required a restart again. The second time, the "installing" process took longer to finish on both computers but finished correctly, restarted correctly and everything went fine. Luckily, on both computers, the second time was a charm and the update installed correctly and was not detected a third time. When I "Viewed update history", the update showed as installed twice with the (2) listed at the right side of the listed update.
Others are seeing the same thing and the explanation is mentioned in the link below:
I'm just posting this so members will know a second "Check for Updates" and install should allow the update to install correctly.
Hope this helps.