That's just the version of the .DLL, but there are many other files that makes the Addon Manager and any other might have been updated as well, that message simply means that, in order to apply the Live Update, you need to exit from FSX and run the Addon Manager installer.
Just trust the Live Update, if it's saying there's an update, it means there's an update.
Some updates can also be applied without restarting, in this case they are labeled as Couatl updates rather than Addon Manager update.
It's explained in detail on the manual, in the "Live Update" paragraph.
There's no need to redownload the Addon Manager installer, running it should be enough.
