Sorry, i should have included some info in my first post. i have a galaxy s7 running android 6.0
good suggestion! i just ran a few tests and you're right. i usually have my camera icon in the lower right so i removed that icon completely and installed a small app to test and the icon appeared in the bottom right where the camera icon was.
so i did some other tests. i moved icons into the 2 open spots and then got some other test apps and they appeared in the bottom right (which was empty since i uninstalled he previous app)
so it's almost if there is some invisible icons just sitting there.
i also just tried to move some of my existing apps into those blank spots and they moved there just fine, then i removed those icons and installed a test app again but it still moved to a new page.