Originally Posted by one-L
[...]Otherwise, the carbonation is a function of set CO2 pressure and temp of the liquid. It shouldn't be dependent on the volume in the keg.
It takes time for CO2 to diffuse down through a still column of beer. And of course the Out dip tube picks up at the bottom of that column, the last of the beer to reach carbonation equilibrium. So volume does matter.
If one starts drawing pints before a keg has fully reached the carbonation level determined by temperature and pressure, one can expect the apparent carbonation to improve with time...