Well 1 pound a week is a steady weight loss, so thats 9 pounds and if you are 100% on the plan and eating lots of free foods and exercise, then a few weeks you may lose the extra to lose 1 stone.
I would say, aim for the 9lbs and any more is a bonus! Im a 1lb plodder and happy for that to happen.
I have found that in the past if I set myself a goal and I dont reach it Im really upset and think whats the point?