Spike during beginning of fertile period

Hi ladies! any idea what the random spike could mean mid-fertile period? Last month it was pretty stable throughout and then increased afterwards. Last month I think I ovulated later then the app told me based on my temp charting and symptoms I was having (cramps moving from left to right until they became more like mild period cramps a few days later). I'm attaching my current months chart. Any ideas how I need to read this?? And, today was my peak opk result (non-flashing smiley), and was blinking for 6 days in a row. Still learning...