Any working breastfeeding moms, please help!

I will be going back to work the 28th, my baby girl will be 3 months on the 21st. I do not know how many ounces to tell the baby sitter to feed her at each feeding p!us every feeding is different. And when my breastfed baby gets a bottle she will guzzle it down so fast and want more cause she's used to working for it. Any advice to the working moms who have been through this???