Starting to bottle feed (expressed milk) my EBF baby - how much?

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My baby boy turns 1 month old tomorrow so we’ve decided to start bottle feeding once in a while to give me a break during the night, give hubby the opportunity to feed/bond with baby and get baby used to bottles in case I ever need to go somewhere and can’t BF him.

I’m just wondering how much hubby should feed him? I’m so nervous about overfeeding him 😬 Any other tips?