A gradebook in Moodle is a dynamic table containing rows (students) and columns (graded activities). The aggregation of grades in a gradebook can be set in many ways. The one we recommend is weighted mean of grades. This means that an assignment or quiz after grading will be scaled by a certain percentage (based on the syllabus). In case an instructor wants to group multiple items/activities of the same type, he can create a category (container) with an aggregation set to simple weighted mean of grades. By this aggregation, all grades falling under this category will be summed up and then scaled to that percentage.