Can you mix pumping sessions?

Pr

Scenario: I used my Haakaa pump around 2:30pm got maybe about an ounce. I have it in the fridge in a bottle now. Now at 5:00pm I have used it again & got another ounce. Can I put it in the same bottle from earlier? I only have 2 bottles that were gifted to me. Since I was planning on breastfeeding I didn’t want to stock up on any.. please help me with advice on how I can store my Haakaa milk!