Hi Wahine,
I used to have one of those scales you're talking about with the little lines and if I "leaned" just the right way I could get a nice low reading. It helped that it weighed good bit lighter than my doctor's scale too ... until I had to go to the doctor's of course.
Anyway, my in-laws recently moved in with us and brought a good sturdy Sears digital scale that they've had for years that weighs to the 1/2 lb. and is right on the money with the doctor's scale, so I am happy with that, knowing it's accurate. I have found that I can get 2 or 3 different weights in succession and when I do, I ALWAYS take the lowest.
Hope that helps.