Which one is +OPK?

So I got a line that was pretty dark at 6pm last night (CD 14)

But today at 1pm I took another one (CD 15) and the line was even darker. Darker than the control line. So my question is.. which one would I consider positive? If a got a line as dark as the control line then that is positive, but why did I get an even darker line today? This is only my second month using these strips. Thanks in advance for any advice!