Before commenting directly about Mark 6:30-44, allow me to direct your attention to two Old Testament stories.
1. The first story is found in 2 Kings 4:1-7 and concerns the widow of a prophet whose creditors were about to foreclose her outstanding debt. Additionally, her two sons were to be carried away as slaves. Beside herself, the widow cried out to Elisha for help. Elisha asked her if she had anything in the house of value which might be sold to provide money toward the debt. "Only a partially filled jar of oil," she answered. Elisha surprisingly instructed her to go throughout the community collecting jars to be filled with her oil. We are probably safe to assume that if she did not feel rather foolish, there is a good chance her sons did. Here she went, gathering empty jars to hold the little bit of oil which did not nearly fill the jar it was in. When it was all said and done however, there was more oil than jars to put it in, enough money was available to pay the creditor, and the excess was sufficient for the widow and her boys to live on.
2. The other story is also found in 2 Kings and again deals with excess. A man brought Elisha twenty loaves of barley bread and was instructed by the prophet to feed a rather sizeable gathering. The man asked, "How can I feed 100 men with only twenty loaves of bread?" To make a long story short, let’s read the conclusion of the account: "Then he set it before them and they ate and had some left over" (2 Kings 4:42-44).
The account in Mark 6:30-44 bears striking similarities to the incidents mentioned above, especially the latter. For this reason, the feeding of the 5,000 is understood by many to be Jesus’ confirmation that his ministry was in the prophetic tradition of Elisha and under the authority of God. That is one way to interpret the miracle.
Another explanation was offered years ago by the distinguished Christian, Albert Schweitzer, who believed that the feeding of the 5,000 was an "eschatological sacrament" which was in fact a foretaste, or preview, of the greater feast to be held in the approaching Kingdom of God.
Of course, the simplest explanation is that Jesus was addressing a specific need at a specific time, and that that is the whole of it. However, let us not overlook the emphasis that Mark places upon the miracles of Christ as signs of his authority. We would perhaps be well within the mark to accept all three possibilities as legitimate.
I particularly like the quantity measure in the Elisha stories, the feeding of the 5,000 and other incidents throughout the Scriptures. The provisions were not merely sufficient for the immediate need, but always resulted in excess. Surely that must suggest something to us of the mind of God. His grace and love are more than sufficient for our needs.