The price of funds at the time which you requested to sell might have changed in value due to the small time-lapse from you making the request, to the AMC actually processing and trading your investment.

For example, you might request to sell your funds on Monday evening, but the request is received on Tuesday when the markets open and the fund units are sold. The value might have increased or decreased at this point since the fund values are calculated on a daily basis. This variation is reflected in the amount that is returned when a withdrawal request is made.