Rookie question

I've expressed a small bottle of milk and stored in fridge overnight, upon looking at it now it seems to have separated - there are yellowish lumpy bits in watery milk. Is that normal? Will it mix back together when I warm it?

I went to ABA website about expressing/storing and the table says freshly expressed milk can be stored in the fridge for 3-5 days, but then the bottom of the chart it shows that if the baby has started to BF to discard EBM. What the?