Six in the fifth place means:
The sovereign I is T'ang the Completer. This ruler decreed that the imperial princesses should be subordinated to their husbands in the same manner as other women (cf. hexagram 11, six in the fifth place). The emperor does not wait for a suitor to woo his daughter but gives her in marriage when he sees fit. Therefore it is in accord with custom for the girl's family to take the initiative here.
We see here a girl of aristocratic birth who marries a man of modest circumstances and understands how to adapt herself with grace to the new situation. She is free of all vanity of outer adornment, and forgetting her rank in her marriage, takes a place below that of her husband, just as the moon, before it is quite full, does not directly face the sun.