clear blue advanced ovulation tests


so I'm wondering why people say to disregard what the test strip says and only go by what is on the display? when negative the test line is always faint, when flashing the test line is medium and when at peak the test line is super dark for me always. but if I would have went by the display last night I wouldn't have known I'm ovulating because I grabbed the wrong display thing and it read at negative but the test line was super dark (this is one from last month where I never ovulated) but I realized it and grabbed the right one and tested on it too and it was positive and the test line was again super dark. it kind of seems obvious that you can tell by the lines.