When thinking about magic I generally like to think of it as "quirky laws of physics that nobody bothers asking why it works", but independently if it's this or truly supernatural, in scenarios where magic exists, when doing something, which part of the act stops being supernatural and starts being normal science? At some point the magic will start interacting with the natural world.

If someone conjures a fireball, is the fire itself (ionised air) being created out of nowhere, or are they actually creating a fuel and a spark and the fire is from normal combustion?

When making something float, are they making the object ignore gravity somehow, or are they applying a measurable force (Newtons) to the object to raise it?

If you do a healing spell, is the spell creating nutrients for the body to consume and heal for itself, or is the spell for fixing the damaged tissue directly?

If you turn something into something else, for example turning some object into gold, is it replacing each atom of the object with an atom of gold (keeping volume), or is it recombining the existing protons and electrons to make gold atoms(keeping mass)?