Every Light level gives a different amount of light points. You need to reach 2000 points to finish the step, and the indicator changes every 200 points. Every 2 hours some activities gets a bonus giving more light. Afaik this isn't tracked anymore, but you can just mix it up once in a while to check.
Feeble 8 points
Gentle 16 points
Bright 32 points
Brilliant 48 points
Blinding 96 points
Newborn Star 128 points