You are really small, so I doubt that your BMR is anything over 1200 kcal. 30 minutes on the elliptical would spend 300 kcal at most. That means a daily deficit of 1500 kcal.
To lose one pound of fat, you need a deficit of ~4000 kcal. If you fast for 5-6 and exercise everyday, you will have a deficit of 7500-9000 kcal, or around two pounds of fat.
Your weight might be lower than that on the scale, but that’s all water, lack of food in your digestive system and glycogen