Small Taming's second line does not correct itself on its own initiative; it is drawn back to the proper course by the companion below it, and Legge's rendering, the second nine undivided, promises good fortune for that return. The brief commentary explains that he returns by the attraction of the line beneath him, and that he is in the central place.
Nine in the second place occupies the middle of Qian, the lower trigram, and though a firm line in an even numbered position is not counted as strictly correct by the usual rule of position, the centrality of the place compensates for it here. The imagery builds directly on the first line: where line one returned on its own initiative, line two is drawn back by that same companion beneath it, so the return becomes a shared, mutually reinforcing motion rather than a solitary correction. Nothing in Small Taming has yet organized itself into active restraint at this height either, and the two lower lines of Qian effectively confirm each other in holding to their own proper conduct.
The picture Legge's commentary gives is one of companionship doing the quiet work that compulsion has not yet had to do. Being drawn back by an ally, rather than driven back by an obstacle, is itself the reason the line counts as fortunate, and it sets the pattern the rest of the lower trigram will continue before the restraining fourth line is reached.