Glow period prediction seems off

Liana
Today is day 28, and no AF in sight. I don't want to get my hopes up, but I'm questioning the accuracy of Glow's predictions. They've been off before...
My cycle has deviated some since I had one of my tubes removed due to an ectopic last year. 
My past 5 cycles were: 26, 30, 28, 31, and 28 days. On average it's 28.6 days until AF. However, Glow is predicting my next AF to come after 33 days. 😳 This is so confusing. 
Anyone else experiencing this?