They have had a history (along with nearly all fork manufacturers) of getting some of the factory oil fills wrong – too much/little by batch.
Generally they will not feel right with the wrong volumes (or feel better as the factory volume was not suited to you as a rider). Oil level is in some cases just lubricant and in others it’s another tuning dial.
The manual will tell you if you need to fill with oil as a factory directive. If you open them and change the oil you can put in the “Factory specified” volume but again with Marzocchi this could be plucked from thin air.