Load Factors R4

I've noticed that whenever I use the default price for new routes, no matter how many seats I have they are always filled (completely green). When I input a new number (even if it's the same amount as before) the load factor changes so that it eaitehr isn't completely full or is filled with a bit of blue. Whenever I reset this though, it goes back to a full green load factor. If I do this, I get a very high profit, but I feel a bit guilty for getting this unfair extra money.

Sorry if it seems a bit weird with the explanation, Idk how to really explain it.