Q: Each monster has an 'Advantage Modifier' listed. Is that just the 'A' for their CAST rolls, or is it their total CAST roll modifier?

A: Similar to the way in which a monster's Resistance Points are grouped together into one lump number to help speed up combat and make the Storyteller's job a bit easier, each monster's "Advantage Modifier" is meant to be a fast & easy lump number that Storytellers can add to that monster's CAST rolls. It does not have to be their total CAST roll modifier. The Storyteller should feel free to include other/additional Advantage Modifiers (bonuses or penalties) if they deem them appropriate.