Method of filling a mold with a glass gob through an opening of the mold, for forming a glass product in the mold, by using a delivery system for delivering the glass gob to the opening of the mold. The delivery system has an inlet, an outlet, and guiding means for guiding the glass gob through the delivery system. The method includes observing the glass gob, at at least one moment and/or during at least one period after the glass gob has passed the inlet of the delivery system, by using an optical imaging device. The method includes determining a glass gob observation result that includes a glass gob velocity, for predicting a glass distribution of the glass product formed in the mold and/or for controlling a next glass gob.