After Jesus fed both the 5,000 and 4,000 with only a few loaves of bread and a few fish, the disciples got in the boat without enough bread for themselves:
17 Aware of their discussion, Jesus asked them: “Why are you talking about having no bread? Do you still not see or understand? Are your hearts hardened? (Mark 8:17)They didn't understand the meaning of the leftovers -- that Jesus would take care of them when they take care of others.
19 When I broke the five loaves for the five thousand, how many basketfuls of pieces did you pick up?”Understand what?
“Twelve,” they replied.
20 “And when I broke the seven loaves for the four thousand, how many basketfuls of pieces did you pick up?”
They answered, “Seven.”
21 He said to them, “Do you still not understand?” (Mark 8:19-21)
The leftovers were for the servers. The first time there were twelve servers and twelve baskets full left over (Mark 6:43). The second time there were seven baskets left over -- the number of abundant completeness. Why didn't they understand that Jesus would take care of them? You can't outgive Jesus; when you spend your life for others, your needs will be met.