There are different ways in which you can score the tests.
You can also score students based on the percentage correct.
Another way, which I find easier and just as reliable, is to score students on the number of problems they get correct.
After students have taken the CBM, I grade them by using the last scoring method. They are graded according to the problems they get correct. If the problem was solved correctly, I place a checkmark in the box. After all problems have been assessed, I add up all the checkmarks and place that number on the top. This score is what I plot on their progress graph, and they also plot on their own graph.