What do measurements of the mass of the Milky Way indicate?

That the mass is far lesser and distributed mistakenly, as compared to what the orbits of stars declare it should be. Stars orbit more rapidly than the mass would predict, particularly out toward the galactic edge. This means that there is more mass than has been measured, and that it is spread out in a huge cloud around the galaxy. This is one of the reasons why scientists believe that dark matter exists.