Scariest math in the world

Please what kind of mathematics is this it worked for me try it,kinda scarry:

Do u knw ur shoe size can tell ur age?
Grab ur calculator nd try dis
Here is how it goes.
1.Take ur shoe size.
2.Multiply by 5
3.Add 50
4.Multiply by 20
5.Add 1015
6.Subtract de year u were born.
U will get 4 digits
De 1st two is ur shoe size nd de last two is ur age.
Plz reply me if am correct!��������