How many progress you get for a chapter or a unit depends on the length and the structure of the course. For every single unit you get a certain progress percentage.The progress ist not related just to the chapters. For that reason you don't get the same amount of progress for each chapter. The progress generates itself out of the units. If a course included x chapters and a total of 10 units, you would get 10 percent of progress for each unit.
The icon in each unit will become from grey into green if you have watched the main resource and solved all quiz questions.
Just the main resources are influencing your progress and are therefore obligatory. Please keep in mind that a lot of the main resources including a quiz or an exercise which influences your progress too.