from https://kellymom.com/bf/got-milk/basics/milkproduction-faq/
Storage capacity: Another factor that affects milk production and breastfeeding management is moms milk storage capacity. Storage capacity is the amount of milk that the breast can store between feedings. This can vary widely from mom to mom and also between breasts for the same mom. Storage capacity is not determined by breast size, although breast size can certainly limit the amount of milk that can be stored. Moms with large or small storage capacities can produce plenty of milk for baby. A mother with a larger milk storage capacity may be able to go longer between feedings without impacting milk supply and babys growth. A mother with a smaller storage capacity, however, will need to nurse baby more often to satisfy babys appetite and maintain milk supply since her breasts will become full (slowing production) more quickly.
Think of storage capacity as a cup you can easily drink a large amount of water throughout the day using any size of cup small, medium or large but if you use a smaller cup it will be refilled more often.