This may explain why her age tends to get younger and younger as documents become more recent. There probably were only so many record agencies who would list her age as "adult" and required a specific age.
It was probably clear to the marrying official that May was over the legal age to marry--and that really was all that was required. If we think about it for a minute, whether a person is aged 40 or 60 does not impact their ability to marry as long as they are single and legally competent to enter into a marriage.
Fortunately most record clerks are a little more particular about requiring an age than this one.
Unless May's new husband didn't know her age either....
Consular Reports of Marriage, 1910–1949. Series ARC ID: 2555709 - A1, Entry 3001. General Records of the Department of State, Record Group 59. National Archives at Washington D.C