that is how sparky will set your pitch counts if you ask for recommended settings under your pitchers' advanced settings.
it is only important because you need to note that sparky will try to match your pitchers' RL innings totals if possible. and also that sparky will ignore your pitchers' IP/G in this scenario.
so, setup men are expected to pitch in 42.5% of your team's games. let's call it 70 games.
if you have a pitcher with 140 RL innings and you put him at SetupA, sparky will assume he will pitch 70 games and expect him to pitch 2 innings per game. then his recommended PC will be something like 25/30 or 30/35.
now, if his IP/G is 1.09 he will get killed by fatigue when he hits 20 pitches, so you'll be in trouble if you listen to sparky.
similarly, if you have a pitcher with 35 RL innings, sparky will expect him to throw 0.5 innings per game, so he'll have a very low PC (probably 5/10 or 10/10). if you wanted him to pitch 1 inning 35 times, he won't do that unless you manually change the settings.