Ok so this thing is a baby height predictor that predicts how tall your baby will be when they're older. It's based on the Khamis-Roche Method. If you google khamis roche method it will be the first thing that pops up. They used to do this by taking x-rays of the child's wrist and measuring bone age and whatnot. But this is a mathematical formula that does the same thing. For boys it can be up to 2 inches off and less than that for girls. You should try it, it's pretty neat!
(P.s, this is my sons predicted height!)
Here is the link: