Hi Broxi. As Channy says, I lost 4lbs in my first week and I've done JUDDDD before. At that time I was losing a good 2-3lbs a week each week but I stopped because I was struggling with the down days.
On a down day, you eat between 20 and 35% of your normal daily calories and there's a calculator on the website Channy directed you to that shows how many calories that equates to. On an up day you don't count calories but each what you want until you are satisfied but not stuffed. I eat out on up days, have puddings if I want them etc.
Down days are not easy but I have found that if I break it down into five little meals of 100 cals each I can do it. When I want something or I feel hungry, I just say "I can have that tomorrow". Often I find I don't want it anyway by the time tomorrow comes. If I do, I have it.