Zhouyi BenyiLine statement
The meaning of this line is not entirely clear. I suspect that the "left belly" refers to a secluded, hidden place. "Catching the heart of the darkened light upon leaving the gate and courtyard" carries the sense of successfully making one's escape far away.
It means that whoever obtains this line through divination should conduct themselves in such a manner. The Li trigram represents the virtue of supreme brightness, while the Kun trigram represents the realm of supreme darkness.
For the lower three lines, light is outside the darkness; hence they carry themselves differently according to their distance and rank.
Six in the Fourth Place, with yielding correctness, dwells in the dark realm but is still shallow, so it can still fulfill its wish to depart far away.
Six in the Fifth Place, with yielding centrality, dwells in the dark realm and is already hard-pressed; hence it is the image of facing inner troubles, rectifying one's resolve, and dimming one's brightness.
Six at the Top reaches the extremity of darkness; hence it wounds its own brightness to the point of complete obscurity, and also harms the brightness of others. For the lower five lines are all noble persons, and only the top line is the benighted ruler.