Amongst others, yes.
> For a given day, will this number increase if new cards are added to the
> database (and their tags are also in the selection criteria)?
Not if cards with grade 0 or 1 or unseen are added, but only with grade >=2,
and then only if they happen to be scheduled for today, and not for e.g.
tomorrow.
> What determines, or triggers, newly added cards to start being shown?
Their initial grade.
> Is there a difference in scheduling between newly added cards which have
> tags that are already in the current selection criteria versus newly
added
> cards which have (introduce) a new tag value too?
No.
> Sometimes I add a new group of cards, exit the program and re-enter to re-
> create the queue, and I wonder why my new cards don't seem to start
> appearing very quickly. I should add that I have both settings set to
"show
> new cards in random order" and "review cards in random order".
If you add cards with grade unseen, 0 or 1, they will start to appear as
soon as you have finished your scheduled cards for today. Of course, if you
added a large number of them, and have set your settings to only have e.g. 5
new cards in your hand at any time, it could take a while for any particular
card to show up.
If you add new cards with grade 2 or higher, they will appear in the next
few days.
Cheers,
Peter