Six in the third place is a favourable line with a bill attached, and a querent who draws it is usually being shown a trade they have made or are about to make. Something nearer, easier and more familiar is set down in favour of something more demanding and further away, and the reading says the exchange works: what is sought will be obtained. The line is unusual in the text for granting the result up front rather than making it conditional.
The condition it does impose falls after the gain rather than before it. Adhering to what is firm and correct is the instruction, and in a reading it means that the new attachment must be kept on honest terms once it starts producing benefits. The failure this guards against is subtle and common: a querent who followed something worthwhile begins, after some success, to treat the association as an entitlement, or to trade on the name of the person they followed.
There is also a plainer use of the line, for querents wondering whether an earlier version of this choice can still be reversed. The second line of the same hexagram shows the trade going the other way, and the fact that both appear in one figure means the text regards the direction as changeable. Setting down the comfortable attachment is described here as a live option with a stated reward, and the discomfort of reaching further is treated as the ordinary cost of it.