Dear Reader,

As you didn't mentioned the complete question but from my point of view the answer of this question upto which I understand is that there is no rules of transfer of marks from any board to another as in your case it is from CBSE to BBOSE if you are carrying compartment in any subjects or not.If you want to clear your compartment exam of maths of CBSE then it will be compulsory for you to appear in compartment exam of CBSE or if you want to clear your class 12 from BBOSE then you have to firstly appear for entrance examination held by BBOSE and then get admitted in cousre and also you have to appear for the examination of all subjects.

Hope this helps to resolve your queries regarding this.

Have a nice day and good future ahead...