Trying for a girl

Okay this is going to sound so dumb. I think I’ve researched so much my brain is fried. As far as trying the Shettles Method (I get it’s not completely scientifically proven, but we just thought we’d try) when they advice having sex 2-3 days BEFORE ovulation are they talking about the one day or your entire fertility window which is like 5-7 days? I want to make sure I time it right! Thanks