I target 500 calories, but have a 600 calorie 'buffer' which helps with the day and planning. On my non fasting days I also still try to watch what I eat and am cutting out bread (my weakness) and potatoes to a point.
What I also love about the diet is it's flexibility. My 2 days can vary each week - I tend to do Monday and Wednesday to get them out fo the way, although last week it was Monday and Thursday. This week due to 'meal related commitments' I am doing Monday and Tuesday, which isnt ideal but I will see how this works.
Ok only in my 4th week, but I am enjoying this lifestyle change and have lost 10 lbs so all is good in the wrold of fasting