What do they indicate at 29.92? How fast do they move (if you take
them
to indicate an altitude?)

If I set the Kollsman to 29.92, the little pointers indicate 1,740 ft.

They only move when I turn the Kollsman knob and the pointers turn in
sync at the same rate as the hundreds and thousands regular pointer
hands move. The pointers do NOT move with actual air pressure changes,
only when I manually rotate the Kollsman knob.