"'When I broke the five loaves for the five thousand, how many basketfuls of pieces did you pick up?' 'Twelve,' they replied. 'And when I broke the seven loaves for the four thousand, how many basketfuls of pieces did you pick up?' They answered, 'Seven.' He said to them, 'Do you still not understand?'" NIV translation
The conversation continues as Jesus reminds them of the fact that He had fed all of those people when it did not seem possible. Their part in the feeding of the people had simply been to deliver what the Lord had provided. All the people had to do was to accept the food as a gift from God. He had been sufficient for the physical needs and He is sufficient for their spiritual need of salvation.
This is a picture of how we are to share our faith with the world. As disciples, we are to simply take the gift that God has provided and present it to those that do not know Him. Then, they can simply accept the gift or refuse it.