I don't know if this is simple enough, but I'll try.
Alright, I just finished up EV training Weavile (6 HP, 252 ATK/SPD). Just to make sure I had 252 in those stats, I used the EV-reducing berries. On my 11th Atk one, it says it has no effect. On my 11th Spd one, it says it has no effect. Is...