Super confused. – Growth: baby & child charts Review

I dont know what to think, or who is “wrong”. Both apps are running WHO percentiles for non-preemie boys. Other app says 6lb15oz is 17th percentile. This app says its .5 percentile. Other app says 21” is 60th percentile. This app says its 23rd percentile. Am I missing something? What am I doing wrong? Also, each time I do an entry, I am asked to rate the app. For that alone, I would give it zero stars. Ugh. Maybe now it will leave me alone?
Review by Jactressk on Growth: baby & child charts.