Well not all potions give the same amount of boost. Maybe it should be a more conditional number. Such as, amount of boost the potion gives divided by 2, then take the ceiling of that. Then you could have it randomly + or - 1 from that number as an anti-ban feature.
Pseudocode:
int drinkPotion
int boostOfPotion
drinkPotion = ceiling(boostOfPotion/2)
int antiBanPotionDrink = genRandNum1-3()
if genRandNum1-3() == 1 then
drinkPotion += drinkPotion + 0
else if genRandNum1-3() == 2 then
drinkPotion += drinkPotion + 1
else if genRandNum1-3() == 3 then
drinkPotion += drinkPotion - 1
end
Hope this makes sense. Just wanted to be extra clear.