Television signals traveling through the atmosphere have highly variable signal losses. You can not depend on a somewhat weaker channel to be reliable enough for recording.
As to the meaning of the 5 green dots, here is my best explanation:
See: Researching DTV Reception
Update: You can look at the reported signal strength on your TV set to get a sense of the relative signal strength of each of your local channels. That will give you some insight into which channels should not be recorded.