it appears to be working properly. under normal operation, the foam will rise in the black pipe, and then spill over into the white portion. what will effect how much comes out is the effeciency with which you match your pump with the skimmer, the water level at which you run it within the skimmer, and how good of a venturi you have running on it.
to make more skimmate, you want to dial up the water level the skimmer, andjusting the air intake to the point that foam is created, but not spilling madly over the lip. to make less foam, but drier, tone down the water flowing into the skimmer. depending on the design, you wither close off the outlet to raise and lower the water level, or you crank up and down the input. there is either a
ball valve one side or the other, or there is a riser tube...
i guess to be more helpful i will either need some pics of the whole unit, or i need to get less lazy and research how your skimmer is supposed to work.