Development Bar

[distant sounds]

I've always looked at this bar not quite knowing how it progresses. Sometimes it's orange, sometimes green. I know that when it changes to green it means the player is progressing, but does it have to go all the way to the right for the player to gain an extra half star in their CA? I haven't found any info about it so not sure how to read it properly, in regards to how my young player is progressing. Even when say a 20yo in my first team gets 23 starts in a season, it will remain orange the whole time.