The Healthy Body Calculator® uses several nutrition science-based formulas. If you are 23% bodyfat, you would not have gotten an “unhealthy weight” message. If you put in just your height and weight, you would have gotten an unhealthy weight message because your BMI calculation is in the “overfat” range as you indicated. BMI is a calculated health risk assessment based on an average (not lean) person. If you have had your body fat measured at 23%, you need to include that figure in the calculations.
If you would like your current body fat included in your calculations, you need to include it in the body fat section on page 2 of the calculator. You can also include a body fat goal and the calculator will refigure your weight goal based on your body fat goal.
So try it again and include your current body fat to get a weight range based on your current 23% body fat.