Bottles at Daycare

I know that breastmilk changes to accommodate baby’s needs & because of this, the quantity of breastmilk baby eats per feed really doesn’t need to change (not like formula fed babies, where they number of ounces they get keeps going up as they grow). Currently I’m sending 3.5oz bottles with my son to daycare (he’s 3.5 months old). The provider said something about him growing more & needing bigger bottles. I don’t want to come off as a know it all mom, but I think they don’t have much experience with breastfed babies. So basically I’m looking for a article or something I can print off and give them to help explain this - anybody know where I could find this? Thanks