We'd have to know both the wet mass and the dry mass to figure that out. They mention 10 kg which I assume is the wet mass but don't give another mass number.
For electric thrusters on cubesats, you can basically ignore the mass variations for most high level calculations. Propellant mass is so little and the specific impulse so high that unless you are using all the propellant in one giant maneuver the difference will be minimal.
But it does not eject any mass, so it's all dry mass once in orbit, I assume.
Hall effect is pretty weak, though.
It does eject mass just like any other thruster. It is just a lot less mass ejected at a lot higher velocity which is why the efficiency is higher.