Just really thinking about Jesus feeding the five thousand is mind blowing. For one thing, our deacon told us in a recent homily on the subject that only the men would have been counted. So when including the women and children there may have been actually ten thousand or more people there. Barclay tells us that each loaf was not what we would think of as a loaf of bread but more like a small roll. Not that it really matters but it just signifies God's abundance even more. I also liked this commentary about how the miracle of the loaves connects with the Last Supper.
The miracle of the loaves looks both to the past and the future.
(1) It recalls miraculous feedings from the OT, like the heavenly manna God provided for Israel in the wilderness (Ex 16) and the multiplied loaves and leftover baskets provided by Elisha (2 Kings 4:42-44).
(2) It also anticipates the later institution of the Eucharist, where the same string of verbs (taking ... blessed ... broke ... gave) is found together, something that only occurs here and at the Last Supper (14:22; CCC 1335).
The Gospel of Mark(The Ignatius Catholic Study Bible)