The Over Allocation Level
This level determines whether the allocation of peer assessments to the class is balanced or not. Here the term "balanced" applies to the number of times each student submission is allocated for (peer) assessment. When the Over Allocation Level is set to ZERO, all the submissions are allocated the same number of times, that is, the allocation is balanced. When the Level is set to ONE then some of the submissions may be allocated once more than other allocations (and it follows from this that some of the submissions may be allocated once less than other allocations), that is the allocation is unbalanced. Similarly if the Level is set to TWO then a greater unbalance is allowed.
Ideally all peer assessments should be balanced. However, the disadvantage is that some students will not have their full quota of submissions to assess until AFTER the last student has submitted their work. When the Over Allocation Level is set to ONE, then most students will find that they have their full "quota" of submissions to assess and they do not have to wait for late submissions. Waiting for late submissions should be even rarer when the level is set to TWO.
So in a Workshop assignment where the number of peer assessments is set to 5, and there is no concerns that some of the submissions will be (peer) assessed 4 times, some 5 times and others 6 times, then the assignment will "flow" smoother and the students will not have to wait so long (if at all) for others to submit work if the Over Allocation Level is changed from its default value of ZERO and set to ONE.