Wow, 200 birds is a lot to mix fermented feed for. I occasionally make it for up to 70 birds but they have dry available too so in case I can't keep enough FF on them, they still have something to eat.
What kind of feeders are you using to feed 200 birds FF?
They won't eat a lot at that age but every day, their appetite will grow. Whatever they eat now, they'll eat a lot more in a couple weeks.
Generally speaking, you want them to have food available all waking hours. If their crops are empty, they're hungry. With fermented feed, you'll have to replenish it a couple times a day. In the brooder, the warm dry environment will dry it out and harden it to the point they won't be able to eat it.
Whatever amount of dry feed they eat, depending on your feed containers, you may only use about 70% of the current consumption FF because of less waste.