In Savage World, every 1 Power you maintain is a -1 to your casting roll. If I have a power that targets 5 (and which requires maintaining), is it considered as maintaining 1 power or 5 powers?
One power. Basically you can count your castings. So if you've got a multi-target spell like Burrow, you can maintain it on everybody as one spell (you're only casting the spell once, you're just hitting extra people thanks to the Additional targets clause). But if you cast Deflection on 3 people, that would be 3 spells being maintained (since you had to spend 3 actions to do so, rolled to cast three times, etc).