DPO? πŸ˜’πŸ˜’πŸ˜’πŸ˜’

When people ask how many 'dpo' are you.... Do they mean from the beginning or the end? Or middle of ovulation? It's so confusing to know! My period is due the 16th I ovulated between 28th-3rd... Glow said not to test today, so I did a test and BFN πŸ˜•πŸ˜•