Wondfo opks

Kerri • 17 months ttc, 4 cycles fertility treatments just got my + hpt today!!!
Just wondering something. I have been using these opks and I always get two lines, they get darker and lighter but I'm just wondering if I'm the only one or should I only be getting two lines when I'm close to O? The test line did get darker at O last month. But this is only my second month using them....