that's the combined AUM size of available institutional equity in those geographic areas, boiled down from perhaps 1200 individual US investment companies.
I imagine they were all invited (in the chosen cities), however of those who RSVP'd, the make-up of who POET is presenting to is not public information (nor should it be expected to be).
and yes, on the map St. Louis has a typo.
GLAL,
R.