Im getting Additional Updates available in Windows Update

How exactly does this work and what is the best way to deal with these updates?

This is more info on what Ive just seen on my PC
I have clean installed 1903 recently so Im still getting used to the way Windows Updates works with 1903.
I don't manually checked for updates. I just let Windows Update update automatically when Windows Updates are ready. However, This morning in Windows Update I got Updates Available with a yellow exclamation mark. Directly underneath the message was the following :-
2019-06 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows 10 Version 1903 for x64 (KB4502584)
Status Pending Download
Updates are ready to download
and a grey Download button

All previous updates have been pushed to my PC automatically as normal. Is there a reason why this update hasn't downloaded automatically? Why am I getting a Download button?..What should I do with this Update? Should I click on the download button or wait for Windows to automatically install it?

Underneath that there is a line and the following :-
Additional Updates Available
2019-06 Cumulative Update for Windows 10 version 1903 for x64-based Systems (KB4501375)
Download and Install Now in blue

I have checked up on what has been fixed etc with the update. But why am I seeing Additional Updates instead of them being installed automatically? What should I do with this and any other Additional Updates that appear in the future?

"why am I seeing Additional Updates instead of them being installed automatically? What should I do with this and any other Additional Updates that appear in the future?"

1903 introduced new WU features, like the ability to pause installs for 7 days, etc. WU will check daily or you can check manually. Those two update alerts are to let you know that you can download & install on Your time vs auto install in background and restart when inconvenient which many complained about in past. I can only speculate because I manual check often but the yellow is a critical update while the blue is a Build update.

Bastet said:

I would click on the install now button, usually if you have auto download set it will do so but some updates will require a manual confirmation to update/install.
Eventually these updates may download/install themselves.

So are you saying that even though I have auto download set that some windows updates still require you to click on download as with the 2019-06 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows 10 Version 1903 for x64 (KB4502584) where I got
Status Pending Download
Updates are ready to download
and a grey Download button that needed selecting beneath it

Yes, I see the same, most updates will install automatically eventually.

Are the Additional Updates the same thing as what used to be known as Optional Updates? What happens if I don't install any Additional Updates that are offered? Will they eventually be installed automatically at a later date ...maybe on the next Patch Tuesday for instance. I want to limit any risks with windows updates and make sure that I don't install an update that might have possible problems. On the other hand I want to also make sure that I install every necessary update that should be installed.