Glow gives different info on 2 devices

I downloaded the glow app on both my iPhone and my Note 3. I added the exact same information in both and got totally different results. Doesn't make sense. It has my fertile days off by about 3 days and I'm not sure which one to go by. 
​Before I discovered Glow I had a few different tracking apps as I've never really kept track of my cycle ... it's all so new and I was trying to decide which one was best but they all seem to give different results. So confused and not sure which to go by. 
​Now with Glow giving two different results I'm even more confused than ever ... Anyone else have this issue? 
 

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