Checking is moderate and there is also step marking .CBSE provides a  proper guidelines to the checker and they are asked to follow it.
As per my experience you cannot get less marks then your acceptation if you have genuinely calculated it checker are quite liberal regarding this because any mistake  may create problems for the checker .CBSE is quite serious regarding this so checker also tries not to indulge themselves in this.
But somehow if you feel not gratified with your marks then you also have a policy to challenge your copy.
Thankyou!

It is going to be tough. Moderation policy has been removed.