This is the maximum grade given to the assessments make by students of their own and/or other work. That is, the grade for their assessments. The actual grades for an assessment is calculated by the workshop module by comparing that assessment with the "best" assessment of the same submission. The "best" assessment is the one which is closest to the mean of all the assessments. (This is a "weighted" mean if the teacher's assessment are given a weight greater than one.) Note that if there is only one assessment of an submission, that single assessment is taken as the best. If there are two assessments of an submission, both are considered "best". Only when there are three or more assessments does the module start to make distinctions between the assessments.
This grade is sometimes called the "grading grade" and is not the maximum grade given to the work, that grade is called "Grade for Submissions".
A student's grade for the workshop is the sum of this grade and the grade for their submission(s). Thus if the (maximum) grade for the Student assessments is set at 20 and the (maximum) grade for submission is set to 80, then the (maximum) grade for the workshop is 100.
This value can be changed at any time and the effect on the grades seen by the students (and the teacher) is immediate.