There is no specific guideline for how many evaluation points you should be making, as the essay is not typically marked on quantity. That being said, one student can be putting forth 1 point and another student putting forth 3 points, and sometimes, the student with only 1 could potentially get placed a higher band. This is sometimes the case as the student who only put 1 point developed their evaluation to the question's demands, did this at a good level of quality and showed a better understanding than the student who put forth 3 points that were lacking in quality and clarity.