so really, ares would get 200% extra and the whole team would get 60% more (70% if the friend eidolon counts)
This is a math thing. You get 10% from each of 6 eidolons (lets say 1000 ATK each, for 6000 total), you get a bonus (1000 * 10%) x 6 = 600 ATK. You could not say you get 60% of anything without it getting weird.