What is the meaning of Matthew 15:37-39?

37 And they did all eat, and were filled: and they took up of the broken meat that was left seven baskets full. 38 And they that did eat were four thousand men, beside women and children. 39 And he sent away the multitude, and took ship, and came into the coasts of Magdala. (Matthew 15:37-39 KJV)

William Burkitt’s Commentary

They did all eat, not a crumb or a bit, but to fulness and satisfaction; yet seven baskets remain; answering the number of the loaves, as the twelve baskets in the former miracle answered to the twelve apostles: in both, more is left than was at first set on: it is hard to say, which was the greater miracle, the miraculous eating, or miraculous leaving. If we consider what they eat, we may justly wonder that they left anything; if what they left that they eat anything. (Dr. Fuller.)

Observe lastly, Christ would not have these fragments lost but gatherd up; the great housekeeper of the world will not allow the loss of his orts. O how dreadful will the account of those be, who have the large and plentiful estates to answer for as lost, being spent upon their lusts in riot and excess! Dr. Fuller