Below is a certified copy of the delayed birth certificate for my mother, Mrs. Hattie Lee Peters Clark.  Although this delayed certificate of birth states that she was born May 5, 1913, it is my belief that her real date of birth is May 5 1917.   As we all know many black births went uncertified because of the practice of midwifery, and many black midwives were illiterate and could not read nor write.  So, my mother literally had to "make up" a birth certificate. 
There was nothing in existence to prove the correctness or accuracy of this birth certificate.  Therefore, it is my belief that she may have believed it to be to her advantage to set her age to make her appear older than she actually was.