Mary Lane Button -- I'm trying to do the math!

Looking at various documentation, my great grandmother, Mary LANE BUTTON , has a birth span from 1869 to 1875 (a six-year span).  The more I find, the more questions I have . . .

Below is a letter from 1935 that my paternal great-grandmother Mary BUTTON sent to the county clerk in Georgia requesting a copy of her marriage record to my great-grandfather Henry BUTTON.   In the letter she states that they were married December 24, 1883.  She needs proof of her age to get "old age assistance". Following that is the response from the clerk's office.

Mary LANE BUTTON inquiry for marriage license (24 Jan 1938)

Response to Mary LANE BUTTON from Deputy Clerk, Bibb County, Georgia (27 Jan 1938)

Marriage License of Henry Button (Burton) and Mary Lane
from

• Georgia, Marriage Records From Select Counties, 1828-1978

The 1910 U.S, census lists the number of years married as 26 years which would be 1883  --  another verification of their marriage year.  My great-grandmother's age is listed as 41 which would make her birth year 1869 and she would have been 14 years old when she was married.  She is living with her husband, Henry BUTTON and five daughters  --  Florence, Ida B, Annie M, Bessie, and Verna E.  There is also an 18-year old niece, Fanny GROSS.  Residence: Macon Ward 1, Bibb County, Georgia.

In the 1920 census  my great grandmother's age is listed as 44 --  three years older in ten years  --  making her birth year 1876.  At this time she is a widow living with her so-in-law and oldest daughter, William and Florence BURKETT and their infant son, Joesph.   Also in the household are Mary BUTTON's two young daughters, Bessie and Lizzie (Verna). Residence:  Macon Ward 1, Bibb, Georgia

On to the 1930 census, her age is listed as 59 making her birth year 1871.  She is living in Detroit Michigan with her son-in-law and daughter, Charles and Ida B. RUSSELL and their adopted daughter, Cauurn (?) Johnson.

Of course the last available census is from 1940.  Her age is listed as 72 making birth year 1868. She is living in Detroit with her son-in-law, Charles and two lodgers.  (Her daughter, Ida B. BUTTON RUSSELL, is deceased.)

Below is the New York State Death Certificate  for Mary BUTTON.  The year of her birth is given as 1875  --  which would have made my great grandmother 8 years old when she got married!  Informant was her daughter, my great-aunt Anna Mae DAVENPORT.  At this time she was living with her son-in-law and daughter, Richard and Anna Mae DAVENPORT in Buffalo New York.

In each of the census years, I know of every one who is listed as members of my great grandmother's family  --  initially husband & children.  Later as a widow, she lived with her adult children.

I have documentation through census records and city directories that my great grandmother, Mary LANE BUTTON lived with each of her daughters at various times and for some reason I find that very comforting.  I just wish I could find out her birth year!