Yeah there are two kinds of percentage multipliers, one is Star Count, the other is Card Count.
Take TempleShooter card for example.
Templeshooter Card : [Card Slot Equip] Missile attacks have a [card count]% chance to silence for 5 seconds
The chance of this effect is decided by “Card Count”. In this case, the number of star on the card does not matter at all, so equipping 1-star card and equipping 10-star card give the same 1% chance.
What’s worth a mention is that there are some card whose effect chance is decided by “Maximum Card Count”, (@Doddler omitted these) like Harpeia Card, Mineloader Card, Manticen Card. These card effects are mostly about some strong abilities, such as Recovering SP, Increasing Movement, Reflecting Damage. I guess these cards can not be stacked; that is to say, only the card with the most Star counts.