Discrepancies

This is my first month using glow and TTC for #1. My periods are consistently early. April 15, may 15, June 8 (thank God! My wedding was on the 13.. period honeymoon would have stunk), July 6, August 6. Glow was off for my ovulation... it thought it would have came earlier. I'm so tempted to test, but I don't know if I should stick with my past record or Glow ' suggestion of the 7th. Would one day really matter that much? Any thoughts?