This is just the primary election to weed out one person, i.e., $10$ people will contest the actual election. You never know how things will pan out in the actual election. Top $5$ in the primary need not be the top $5$ in the elections, since in the election, you can only vote on $3$ candidates (in fact you rank the three candidates), as opposed to primary where you can up/down vote on any number of candidates.
You may also want to look up the this post, where I proposed to have $5$ moderator spots as opposed to $4$.
Further, Anna Lear in her comment here has also mentioned that if the SE team feels it is necessary, they might appoint more moderators using the most current election result
and this will be announced on meta in case new moderator/ moderator spots are added.