Sometimes the link between two organs gets blocked. If so, using the exit and entry points may clear the blockage.
Element Points and their Chinese Medicine clock times
Some acupuncture traditions consider that treating an organ’s element point during the organ’s clock time makes the point more effective.
For example, your Lungs come under the Metal element or phase. So treating Lung 8, which is the Lung channel’s Metal point, would make it work more effectively if treated between 0300 and 0500. Of course, there hasn’t been a lot of research on this particular point in that regard because most acupuncturists are asleep then.