Let me know if you ever get a knowledgeable answer to your question. My great grandfather and great grandmother have this same notation on their marriage record. They were about 27 & 25 when they married, so in their case it didn't have to do with age. On the same page as their entry is another couple with instructions to not publish. The brother and wife of that same great grandmother also have instructions to not publish their marriage info. He was 27, though his wife was 19. On the same page as them is a fourth couple with "do not publish." These are all in Muary County, Tennessee.