Did you ask for the calculation to your Personnel Department? What did they say about it? It is always better if you ask it to the Officer who prepares the pay and if you fee something unfair talk to us. Moreover, you have not said what amount you have received. Normally, if the increment is Rs 2000 per month, there should be deduction of Rs 240 towards PF on that amount and if so, you will not get Rs 4000 for two months but will get Rs 480 less than that, or Rs 3520. If the amount is less than this, you can ask the Personnel Officer and then let us know.