Your post is not very clear. Are you trying to say that employee did not complete two months notice and completed one month notice only & you need to communicate to him about adjustment of one month salary against shortfall in notice?.
Please ensure in the appointment order/contract of employment order issued to employee 2 months notice period is mentioned and also Management's right to forfeit salary in lieu of shortfall notice. If such clause is there in the appointment order then you present as below :
"As per the clause no_ of your Appointment order signed and accepted by you, your one month gross salary of Rs.___has been adjusted against shortfall in your notice period of ___ days"