I believe it goes by percent of your original body weight...there is not a set number of pounds. For each person, that answer would be different. And, I apologize, I don't know what that percentage is.
A weight watcher website might have that information.
Side note: I got food poisoning once - on New Year's Eve I awoke at midnight and threw up all night long until morning. I was so ill I thought I was dying - literally. At 3:00 in the afternoon, I was able to get up out of bed. I weighed myself. I had lost 6 1/2 pounds.
I assure you - that was TOO MUCH!!!!!