A total of 639 Fine Gael figures are entitled to a vote in this afternoon's presidential election contest.
But not everybody's vote has the same value.
Fine Gael's electoral college appears complicated but essentially involves merging three votes into one result.
The 97 Fine Gael TDs, senators and MEPs making up the parliamentary party will have 70pc of the votes. The 22 members of the executive council will have 10pc of the votes. The 520 members of city, county, borough and town councils and Udaras na Gaeltachta will have 20pc of the votes.
Following the first count, the number of votes in each case is ascribed a percentage value. The three percentages are then added up to give a total.
So if half the parliamentary party votes for Mairead McGuinness, she gets 35pc of the total. If half the executive council votes for her, that's another 5pc, and if half the councillors vote for her, that's a further 10pc.
All told, that's 50pc of the vote.
After the first count, the lowest-placed candidate is eliminated and the second-preference votes for that candidate are then counted and distributed.
Again the votes are ascribed a percentage and totted up.