I believe there may be a bug in the interaction between future sight and pokemon with the ability unaware. I tested a battle against my friend to see how future sight and unaware should interact when the future sight user boosts it's stats, and it appears that future sight's power increased after a calm mind boost, which does not match what the calc says is possible.
https://replay.pokemonshowdown.com/gen8ou-1462984459-oky1jntkbxa0oc4k1mxlm7ezvuivtubpw
On turn 3, clefable took 52% damage from future sight under psychic terrain. According to the calc, using storm zone's spread that he showed in the battle, this makes sense and appears to be working properly.
252 SpA Tapu Lele Future Sight vs. 248 HP / 204+ SpD Clefable in Psychic Terrain: 205-243 (52.1 - 61.8%) -- 97.7% chance to 2HKO after Leftovers recovery
However, after I used calm mind, and after psychic terrain ended, future sight did 60% of damage. According to the damage calc, this should not be possible.
+1 252 SpA Tapu Lele Future Sight vs. 248 HP / 204+ SpD Unaware Clefable: 159-187 (40.4 - 47.5%) -- guaranteed 3HKO after Leftovers recovery
and yet, 60% is a damage roll that would have been possible vs a magic guard clef with his given EV spread ((+1 252 SpA Tapu Lele Future Sight vs. 248 HP / 204+ SpD Clefable: 237-280 (60.3 - 71.2%) -- guaranteed 2HKO after Leftovers recovery)). However, this is an unaware clef, as revealed in the replay, and for some reason it took the boosted damage anyway. I tried looking into this online to see if there was a unique mechanic with this interaction, but i wasnt able to find anything
BUG STATUS: FIXED by pyuk