Timsmoms it's an interesting question, I do not know the answer.
The lactating breast is always making milk, and in normal circumstances it will make more milk the more often milk is removed. So personal breast milk storage capacity is not typically something that is ever known nor needs to be known to the breastfeeding mother. Certainly especially in the newborn stage OP is asking about, the important thing is to nurse frequently.
Shootthepigeons, it can be so concerning when baby seems fussy or unsatisfied. But please be assured it is normal for a newborn to need to nurse very frequently. It is normal for a newborn to cluster feed for long periods, to be fussy, to comfort nurse, and to not go any particular longish length of time between feeds.
You tell a breastfed baby is getting enough milk by weight gain. If a baby is getting enough milk at the breast to gain normally, there is typically no need to pump or bottle feed.
Kellymom has a really good article about the early weeks. It details up to 6 weeks of age, but the newborn behavior it covers is normal for at least the first 3 months in my experience: http://kellymom.com/bf/normal/newborn-nursing/
Please let us know if the info we are providing is helpful, and please let us know if baby is not gaining well, or breastfeeding is in any way uncomfortable for you.