abilityIndex parameter of GetAbilityIdByIndex()

[QuantumPie]

For the add-on I'm currently developing, I'm using EVENT_EFFECT_CHANGED and I want to compare the 15th parameter (abilityId) to see if that ability is slotted on the users bar (represented by a 2d table). It seems like GetAbilityIdByIndex() is a function I could use to populate the id for each slot on the bar. However, I don't know what the abilityIndex parameter is, or if I can even specify which bar to check (as opposed to function GetSlotBoundId(number actionSlotIndex, number:nilable HotBarCategory hotbarCategory) where you can specify slot and bar)