FDs are: . normal supper on the NFD before. . 500 cals total on the FD . normal breakfast and other meals on the NFD
So the period of fasting is much longer than the 24 hours you are considering. A 24-hr fast can be ok for maintenance; also men are often able to lose on it. However, women usually have slower weight loss with this system.
I suggest that today you try to eat 500 -600 cals total, either as 1 meal or split between lunch and supper. So, you would have a slightly longer FD than most.
If you really want only a 24 hour FD, then I recommend you keep lunch and supper to no more than 500 cals each.
See how your weight goes and tweak if necessary. Losing the last 7-10 lb is by far the slowest and most difficult part. Most people have to be quite strict to manage it. Oh and don't forget to measure your waist. That is more important than the scales.