Calculation Confusion

Kelley • Pregnant with first baby 👶🏾, due 5/15/19 ❤️

According to Glow, my EDD is 5/15/19. My LMP was 8/8/18. I know that I got my first LH surge 8/19, and I took another test 8/20 and the line was super dark (that’s also when we BD’ed 😏). So am I less far along than what Glow is telling me? My first appointment is on 10/9, and I’m just curious as to what to expect. TIA, ladies!