Ovulation prediction kit help..

So... I have been using the clear blue advance opk...Had a couple "blinky" smileys.. Then my solid smiley... I have also been using the first response opk. With the clear blue I received the solid but the the first response the hl line did not get as dark as the test line.. This was the darkest the line got... Why one test says Yes! & the other says No...