OPK....started testing earlier than directed and got "high fertility"! So glad I didn't miss my window!!

💁🏼‍♀️Liz • Me: 32 Hubby: 34 🐶🐶🐱 Married since 2015 TTC #1 🌈 MC in March 2017
I bought an OPK a few weeks ago and planned on using it this cycle. 
I know that it directs you to wait until the 10th day in your cycle to start testing but I started testing yesterday (cycle day 8). Yesterday I got "low fertility" which was expected. Today on cycle day 9, I got "high fertility"......I'm so glad I didn't wait to start testing because I would have almost missed my fertile window!! 
Has this happened to anyone else?