Unless someone broke / intentionally changed it, the latest DNAS version won't show those update notice messages and most likely it just needed the DNAS process to actually be restarted for the expected version to be used.
I know some aren't happy with the nature of the messages not going away or the automatic downloading of the newer install files which was by design & doesn't actually involve any form or automatic update process - unless that's been changed with the newer 2.5.x builds.
So if you don't want to update to a newer DNAS either for stability (as 2.4.7 seems to be pretty good compared to 2.5.x) or just not wanting the chance of having adverts forced into their stream(s) (as happened not long back from a 'testing error'), it's possible to remove it via some simple css tweaking by using the DNAS's
admincssfile option to load a modified copy of the default css response from the DNAS
-dro