A dispensation is not required for 4th degree consanguinity. There are explananations, some with charts and tables of relationships on some FH websites.
I discussed this with someone on this website recently and have posted links to websites. See Kilmovee parish, Mayo. Topic is "James Marrion 1820-1895". It's one of the most recent threads for that parish, begun 21st Jan 2019.
P.S. Having now peered at the marriage register I see dispensation mentioned. Several other marriages on those pages also mention dispensation. There were various reasons why a dispensation was required for a marriage in a Catholic church. consanguinity and affinity are two. Others include: marriage during a forbidden time (Advent or Lent); dispensing with reading of banns on 3 consecutive Sundays; marriage in which one spouse was not a Catholic. A resume of Catholic Canon Law cites 28 reasons! I can't read the word after dispensation in this case.
"There maybe records where 4th degree was stated but dispensation was not required." Topic "Dispensations in the Catholic Church " on GenProf www.genprof.net/marriage-dispensation-in-the-catholic-church
"The Concepts of Consanguinity and Age of Majority in Genealogy" by Dan MacDonald
www.islandregister.com/consanguinity.html
This focuses on Prince Edward Island but has relevance elswhere.
"The priests were supposed to record all relationships of the fourth degree or closer" ... "As well, each priest used slightly different terminolgy in records"
"The power to grant a marriage dispensation was held by the diocese (i.e. Bishop/Arch-Bishop) ... However priests were sometimes extended the powers to grant dispensations to a particular degree without having to apply to the Diocese in every case."
The point is made that a priest didn't always record information accurately and that he was reliant on information given to him by the couple, which may not have been correct.
The writer suggests familiarising yourself with the priest's style and terminlogy by browsing other entries in the register.
Rules on consanguinity have altered over time as have methods of computation, leading to confusion.
Catholic Encyclopedia is online.
A recent discussion about changes in 20thC and earlier historical aspect was "Consanguinity and cousin marriage" on Catholic Answers Forum
2 comparatively recent key dates when considering Catholic canon law on marriage are 1908 and 1983.
https://forums.catholic.com/t/consanguinity-and-cousin-marriage/447200/4
"Marriage dispensations" on website www.arcadian-home.org/marriage-dispensation.html is a brief explanation aimed at family historians. However, the writer has confused affinity with spiritual relationship. (Relationships which are impediments to marriage are consanguinity, affinity and spiritual relationship; spiritual relationship being e.g. god-parent and god-child.)
****
I read witnesses to the marriage as Winny and Hugh McKenna. "Hugone" is a Latin declension of Hugh. His name was declined in 4th or 5th case, depending on whether English translation was meant to read "witness to" or "witnessed by". If Winny had been given her full name of Winifred, she would have been "Winifreda" or "Winifredae". If she had been the bride she might have been "Winifredam". Name (and word) endings change according to context. There are words in this I can't read.
The word curate derives from Latin curatus which translates as cure. Cure of souls means spiritual charge of a parish or congregation. The priest who conducted the marriage may have been a curate and not a parish priest. Was it a chapel in a parish at the time?