how accurate is this "fat loss monitor"

JAGWIRE13579

So my husband brought home this Omron fat loss monitor from work. I think it was pretty cheap. Here's my question for anyone who is knowledgeable about such things. How accurate is this fat percentage? I enter in my height, weight, age and sex then you hold onto each side of the metal handles and it's supposed to tell you what your fat percentage is. Mine is coming up 30.1% and I can't believe that's right. I'm a 42yo 5'6" 204lbs. I have a medium frame and I am not muscular. I do light weights and cardio for 45 min 3X week. I need to lose another 50lbs at least. Wouldn't that be considered 25% of my current weight? I know I would not be down to 5% body fat if I weighed 155lbs. Can someone explain this to me please. I thought women like me should shoot for low 20's for body fat percentage. I'm not going to spend money to find out a truly accurate fat %, I know that involves water tanks and things, I've seen it on TV. I just want to know if this thing is junk or if I just don't understand how this body fat thing works. My main concern is setting a reasonable goal weight for myself. I have been fat since I was 18months old and I don't even know what a healthy weight is for my body. I have heard ranges from 125 to 165, that's a pretty big range. Thanks