Calculation of Gratuity - not taking DA into consideration?

I have joined in the Company on 10.10.2012 and got relieved on 30.04.2018. They have paid my salary for the month of April 2018. As per the pay slip for the month of January 2018 & February 2018 issued by the HR, my basic salary is Rs.13,750/- and DA is Rs.5,500/-. But I was informed by the HR department that the pay slips issued only unofficial purposes and you are eligible for Rs.39,663/- only towards Gratuity amount. They are not taking into consideration of DA of Rs.5,500/-. May I know the procedure following by the HR Department is the correct. Waiting for your valuable reply.

Your company is not following the right procedure,DA should be included.
Speak to them and get clarified further.

Below is the gratuity calculation formula [Section 4 Payment of Gratuity Act]:-
Monthly Salaried Employee
Gratuity = Last drawn wages × 15/26 × Completed years of Service (including a part of year in excess of six months)
Wages = Last Drawn (Basic +DA)
Month = Period of 26 Days
15 days wages = Last drawn wages × 15/26

Dear Mr Prasad, based on the information furnished by you i.e
DOJ:10/10/2012 DOL:30/04/2018 You are eligible for Gratuity for 6 Years (6 Months & above rounded off to 1 Year)

Dear Marlnsprasad_2006,
You said you were informed by your HR department that the pay slips issued only for unofficial purposes. I do not understand the meaning of it. I don't understand how the HR can talk like it. Are they really don't know the law?
You are entitled to get Gratuity as under:
(13750+5500)÷26*15*6= 66,635.
You are advised to give a letter to your company management stating your entitlement as above and request for settlement accordingly. Send this letter by registered a/d. If your company do not settle your claim as per your request then make a complaint to controlling authority under the PoG Act.

Sir, Thanks for providing valuable information. In the year 2017 & 2018 I was granted leaves around 10 to 20 for attending MBA examinations. May I know are they deduct the said leaves from the service period. Sincerely, Prasad.

If it is paid leave, they cannot deduct the leaves from the service period.