Added images are directly visible on website

NGG Version 2.0.17

I create a new gallery (gal1).
I add img1 and img2 to this gallery.
I open the ATP window, select gal1 and do not exclude any image.
=> img1 and img2 are shown on my site (site1)

Now, I add img3 and img4 to gallery gal1.
When I reload site1, I see all four images.

What this implies:
Suppose I have a gallery which I keep uploading images to. Sub-galleries out of this gallery are shown on various parts of my website (i.e., I exclude certain images from being shown).
Whenever I upload a new image to my gallery I need to reconfigure any website a sub-gallery of this gallery is shown.

The better way:
I think, newly added images to an existing gallery should by default be ticked for exclusion.

https://www.ads-software.com/plugins/nextgen-gallery/