Six in the second place means:
Yellow is the color of the middle. It indicates that which is correct and in line with duty. Oxhide is strong and not to be torn.
While the superior men retreat and the inferior press after them, the inferior man represented here holds on so firmly and tightly to the superior man that the latter cannot shake him off. And because he is in quest of what is right an so strong in purpose, he reaches his goal. Thus the line confirms what is said in the Judgment: "In what is small" - here equivalent to "in the inferior man" - "perseverance furthers."