Dear Member,
In the period as shown by you, two different benefit periods falls i.e. first- December, 2013 ending and second -June, 2014 ending. Therefore, in these 2 different benefit periods, the rates of sickness or eligibility to benefits may differ.
Further in respect of payments of Sickness Benefit, the benefit for first 2 days is not paid by ESIC and deducted as "waiting days". So, I think, your calculation may not be correct.
It is good aspect that you are calculating the benefits amount payable to employee under ESI Act. However, I will suggest you to ask the employee to show the slip issued by ESIC Branch Office regarding payments of benefits as and when he approaches to ESIC for receiving his cash benefit. From slip of benefits paid to the employee, you can get correct idea as to how the benefits are calculated under above Act and what were/are his rates of sickness benefits.