Glow has wrong cycle dates????

Shelbi

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​So, I have AF every 28-29 days. Usually 28 on the dot. First day of my last cycle was 7/30. Meaning my next cycle should be on 8/28. Why is it saying that I should start 8/26? Not too far of a difference but it does make a big difference when TTC and charting. Any one know why it's showing wrong dates??