Red dot showing in the software update icon but already updated

I just updated my Macbook to the latest version of Mac OS: Catalina 10.15.4.

However, I noticed that in the system preferences, there is a red dot on the software update icon, but after clicking it, it says it is already up to date...

So I want to know why it is here and how can I get rid of the red dot?

Thanks in advance!

Fortunately, after upgrading to 10.15.5, the red dot disappears...

Solution 1:

defaults delete com.apple.systempreferences AttentionPrefBundleIDs; killall Dock

This can get rid of it but it will return.

Solution 2:

Try running softwareupdate -ia in terminal to force it to realise it's got them all / install any you may have missed.