Hello,
I have the same issue,
normally the dispensation is given for the degrees of family relatedness - consanguinity and affinity (generation difference since the last marriage of the families).
Impediments in the parish register for St Andrews in Dublin is in a different column from denuntiation and in the denuntiation column is written a variety of abbreviations. Disp is the most common, another has a V and what looks like a number 8, a few have a Tres or Tris (closed e?) which presumably is in Latin and = three.
The Banns in English churches were read three times in church on consecutive Sundays and in more literate times were posted in a public place to allow people to make their own objections. My memory tells me the first had to be 6 weeks before but I am not exactly sure but I am sure you get the gist.
So, I can imagine it is three opportunities to denounce / complain that there is a reason why they should not get married (the impediment) which goes in the next column? However, it makes for confusion compared with rural registers where the degrees of relatedness or dispensation, sometimes from the archbishop where an appeal has been made, were scribbled alongside the entry for the marriage.