How slow or fast do you want to lose weight?
If you want to drop it fast reduce calories-in the words of Dr A "I never said calories dont count! Of course you will lose faster at 1400 cals 20 carbs a day then you will at 1800 cals and 20 carbs a day"
Someone here emailed atkinscenter and they said 10 to 12 x goal weight.
But everyone is at their own pace just depends how long you are willing to wait to get results.