Mana is the current amount of Spirit a creature has. Spirit is the max amount of Mana a creature can have.
When a creature casts a Spell they spend Mana, which d RAWs on their Spirit. A 1st level Spell takes 1 Mana, a 2nd level Spell takes 2 Mana, and so forth. Once a creature's Spirit reaches zero, they cannot cast any Spells beyond Cantrips.
These sliders set site audio only, so you can mix against Discord and other apps (phone volume still caps everything).