Again just thoughts---
Errors have occurred for this woman due to her copying the wrong words , as an illiterate person, on "event" documents. Perhaps this copying was from the marriage on the same page in the book (Hester McCARTNEY whose mother was Mary McCARTNEY)
-She certainly copied the words above hers when she signed her name as DOWDY I think the problem continued with McCARTNEY.
I agree with Cando and Judith, the writing is a struggle for both parties and they may have had little or no idea of the meaning. Many at that time could write a little (name city , age etc.) but could not actually read.
John has taken his previous event documents to register births and the errors have been repeated and compounded as the Registrar just copied them.
Finally, getting to SA, the officiating person (as Cando suggests) actually made a clear verbal inquiry and the facts of name were, for the first time, close to correct.
Sue