This record seems to be in error as dob and marriage are one year apart and neither this James nor Millie was born yet, perhaps a confusion of 2 different families?
James M. Clendenin
Born February 17, 1879 in ,,IL
Husband of Millie M. Johns— married April 14, 1878 in ,Williamson,IL
From familysearch:
Millie May Clendenin
Death 26 Jun 1940 10-2 Williamson, IL
Birth: 01 Dec 1884 New Burnside, IL
Parents Isaac Johns Alice Edmondson
Spouse James M. Clendenin
Burial 29 Jun 1940 Carterville, Williamson, IL Cemetery: Oakwood
US Census, 1910 Herrin, Williamson, IL
SELF James M Clendenin M 33y IL
WIFE Millie M Clendenin F 23y IL
DAU Martha E Clendenin F 5y IL
DAU Lola P Clendenin F 4y IlL
DAU Reba L Clendenin F y 8m IL
US Census, 1920 Herrin Township, Williamson, IL
SELF James Clendermin M 40y IL
WIFE Millie Clendermin F 34y IL
DAU Martha Clendermin F 15y IL
DAU Lora Clendermin F 14y IL
DAU Rebe Clendermin F 11y IL
SON Arlie Clendermin M 5y IL
DAU Sirelny Clendermin F 2y6m IL