You are reading a tafsir for the group of verses 12:65 to 12:66

On reaching home, when they found their money in their bags of corn, they were very happy. They told their father that he should send Benjamin with them. They promised to take care of him. They said that they would bring one more camel-load of corn as his share. They also said that the corn they had now brought was not sufficient for their needs. Perhaps according to the distribution system introduced by Joseph, outsiders were each allowed one camel-load of corn.