Storing breastmilk

I see a lot about how long breastmilk can stay in the fridge/freezer/ room temp. I’m pumping and saving milk but don’t always make enough to fill a bag up. For example, I pumped my last feeding out last night and had about an ounce more of milk than what he’s eating. I want to save that ounce for the freezer but also don’t feel that an ounce is worth an entire storage bag. Can I refrigerate that ounce and add to it and then move it to the freezer? Or does it have to be freezed right away?