The Popular Council in-character consists of two-hundred and fifty-one members. This is far more than the number of players who will ever actually be around to vote. So, instead, each vote cast by a player as a councillor is treated as a sample of their total party's vote, and each party's votes are split up accordingly. How many votes a given party controls within the Popular Council is meanwhile determined by their share of the total vote in the most recent election, which is explained in greater detail
here. Finally, keep in mind that in-character happenings may change this information, so it doesn't hurt to recheck it.