Weight Watchers wants me to eat less than 1000 calories?!?!

I'm 25 years old, female, and I'm currently 147 lbs at 5'3". My job is highly sedentary, unfortunately (computer job). I need to lose about 30 lbs -- my doctor recommended 115-120 lbs based on my body size and my adult weight from about 2 years ago. I'm considering following the Weight Watchers plan based on the recommendation of several people. I had a consultation and was told that my goal points would be 18-20 points per day. A lifetime member told me that one point is roughly 50 calories, more or less. Erm, what? Unless my math is wrong, WW is suggesting I eat 900-1000 calories per day. Is that right, or am I missing something?