The thing with the body fat measurement is that it's always going to be a rough idea, unless you pay to get it properly done.
Apparently, the best thing to use is the calipers, which are a few quid (or whatever your local tokens of value are). I used them for a bit, now I have the flashy scales.
I set myself as female, because my hormones are going that way, but as it's not overly accurate and, like you, I'm having a hard time believing the readings; I just tend to use them as a guide to see how I compare to myself over time, which is, in my opinion, the best way of measuring it when combined with looking at yourself in the mirror and doing the usual measurements....assuming you do the weekly measurement thing, I guess.