she means your LH surge is 24-36 HOURS before you ovulate!
It really all depends on how long your cycles are...I would recommend using an ovulation prediction kit those 7 days (3 days before the 20th and the 3 days after just to be safe). Remember you get your Lh surge 24-36 days before you ovulate! It is good to do the baby dance either every other day or every day for best results!