Being a PhD student, I just finished supervising my first masters thesis. Now I have to assess and grade it. While I have a grading template provided by the university (listing the different aspects of the thesis and points out of X for each aspects), I am finding it hard to estimate how good the single achievements are compared to, well, the general level of theses. If I give full marks now because everything has been done satisfactory and well, and the next thesis that I supervise is even better - I cannot give that one better marks, so it would feel like I misgraded the first thesis.
I imagine that once you have amassed a certain amount of supervised theses, you can estimate the general level of one thesis much better and probably feel more competent to grade fairly and correctly.
But in my situation, having no previous experience in grading, how can I make sure as best as possible that my grading is neither too lenient nor too harsh?