Rubric plugin does not calculate correct final grade

While playing with the framework, I am experiencing really weird results produced by the rubric plugin. I have defined a rubric consisting of three criteria. First two criteria have four levels 0, 1, 2, 3 and the last criterion has three levels 0, 2, 4 (see the screenshot). The maximum rubric score should then be 3+3+4 = 10, the minimum score = 0. The rubric is used for grading an Assignment with the grade 100. Hence the score obtained from rubric should be simple multiplied by 10 to get the real assignment grade.

But I am getting very weird grades like 75/100 (how?) or even 125/100 (wtf!)