The science behind the value of letters (or sounds) is called Numerology.  One can learn an immense amount about the self by studying the value of a name.  For this one would need the full names at birth and the family name as well), as well as the day and year of birth.  If a child is not called by the given name at birth, it means that someone – either the parents or the child, is not ready for all of the lessons it would be calling in by use of the full birth name.