Faulty reading on fertility monitor?

Not sure if my question went through the first time...I am on my first month using the CLearblue Easy Fertility Monitor. I am on day 12 and received my first "high" reading yesterday. I've noticed after removing the test stick from the monitor that there are blue lines that have appeared where I assume the monitor is getting the hormone level reading, but today when I removed the stick the test window was still completely white. I received another "high" reading today, but don't understand how as nothing was measured. Was this a faulty reading and/or test stick?