Now take this with a grain of salt due to me being 6’2’’ and currently just over 250lbs/113kgs (Down from 426lbs/193kgs) so I have no exact idea how long it takes to lose weight in your weight range.
However, with exercise I generally shoot for 1 pound a day with 72’s and that has proven to be pretty consistently accurate at least for me. Some weeks are better, some are worse. When I am committed and disciplined with my fasts and exercise the weight flies off though.
If I were in your shoes I would plan on 26-30 days to lose the 12kg you want if you maintain a consistent schedule of 72s as well as exercising alongside your fast.
Fat people (like myself,) or if you’re >15% BF should lose a pound a day if you do 72+ hour rolling fasts, and pound that snake juice.
*Everyone loses about 2.5 kg in their first three days (all water weight).