It is simply not possible to lose 20lbs of fat in 10 days due to the fact that we consume 2k-3k calories/day and an lbs of fat is 3.2k calories.
So an active male could lose a lbs/day, a woman most likely 2/3 of lbs/day.
In 10 days as a woman you can expect to lose 7lbs.
Everything else you lose is water and discards.