This article will be helpful to read: https://www.babychakra.com/learn/832-all-you-need-to-know-about-storage-of-breast-milk

My Dr suggested that at room temperature you can keep it for 5-6 hours and in fridge, not freezer, you can keep it for 24 hours.

it can be used 4 hours if kept in room temp...and can b even till 24 hours  if stored in refrigerator...