So I’m a bit confused as the measurements to my breast pump containers, bottles, and milk storage bags are all different. When it comes to storing it in the bag to freeze, the milk always measures more than it ever does in the bottles or my breast pump containers. Which should I follow? Which one is more true to the amount?

I use the medela pump containers, my bottles are the Phillips avent and my milk storage bags are baby nova from target.

Any other breast feeding mamas with the same issue?