glow not predicting period accurately

S

this is my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">eve</a> app it is correct as my cycles vary but average 29 days

but my <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> is predicting a 26 day cycle

both have the same previous periods logged. This is super depressing as I have been testing to early....