I was running a server with carrot mode and the setting:
health-formula: 0.8 * baseHealth + max(uniqueFoodsEaten/6, 0)

I then noticed that was weird since you'd get half a heart every 6 food, which was confusing.
So I changed it to:
health-formula: 0.8 * baseHealth + max((uniqueFoodsEaten/12) * 2, 0)

However, this change is not reflected. I've restarted the server, even reset player's food and tried eating them again, but still they always gain half a heart every 6 food now. I'm guessing the original config is stored in the world somewhere?

NEVERMIND, I apparently failed math. Forgot to use floor.