Central Board Of Secondary Education [CBSE] — I have secured less marks in class 10th

Sir I am rishu raj Kaushik from srt school and secured only 47 percent mark's in class 10th so can tell me on what basis did you give me this mark how can you judge me that I can not able.to get a Good mark's in class 10th if I write again exam of class 10th then I will loss my Time for the preparation of class 12 and this will create a bad effect on my 12th