Everyone's physique is different, so we can't agree to measure it, and it depends on what you did in four hours, whether you did it in place, your usual diet control and your own living habits. These are all important factors that affect your weight, so there is really no way to say how much you can lose 1 month. If you can control your diet and have good living habits, you can do 4 hours of aerobic exercise in the gym every day. If the action is in place, the monthly weight 10 kg should be no problem.