What is the "other miscellaneous information" in the Shared Global Area (oracle database)?
That "other stuff" is everything else that the database needs to run.

That's a whole lot of things, most of which you'll never need to care about at all. If you're curious to see what the different memory areas are in your system, you can query the v$sgainfo view and take a peek. Warning: there's a lot of them (1058 entries on a 12c database I'm connected to right now).

For instance, you'll find a "resize operation history" bucket which should hold the information about dynamic resizing operations (which you can query via v$sga_resize_ops view).

Not all of these are documented (mostly because you don't actually care about the majority), but you'll find information about some of them scattered around the web (and occasional bugs related to some of them) if you're curious.

If you're interested about Oracle's memory architecture, the Concepts Guide's Memory Architecture sections is quite detailed already, you'll rarely need to mess with things that aren't mentioned there.