Ugh. Sorry for all my typos. It's my phone.
They're really only accurate in telling you how much HCG is in your urine. My blood HCG was 39 on 11 dpo (3 weeks 3 days), and I got "2-3 weeks" (past ovulation) on a weeks estimator at 14 DPO (3 week 6 days). Then at 4 weeks, 1 day my blood HCG was 520 and at 4 week 6 days I got "3+" week past ovulation on a weeks estimator.
Essentially they're good for letting you kbow your HCG levels are rising. The levels of HCG in your urine are also a little more diluted tha blood HCG.