This screen shows the weight of the currently selected frame, and how it is calculated. Note that the weight of the rest of the bicycle's components can be relatively large compared to the weight of the frame. If you were making a frame for a racing bike shaving off every last gram might make sense, but for recreational bikes those few grams could cost more than they are worth. Try adjusting the material the tube is made of to see what effect that has on the final weight.

If you went to your local cycle shop a light bike might weigh 9.5 Kg, if you were going to win the Tour De France, with a very expensive bike, then it might weigh 7 -8 Kg with a frame weighing 1.75 Kg plus extra light wheels, accessories etc.