I purchased digital gold for X amount. But the value is seen as Y in my gold locker. Why?

The buy and sell prices are different owing to the various costs involved in procuring and securely storing the gold along with the buy-sell spread in the commercial bullion market. When you purchase X amount of gold, it includes GST of 3% and the gold will be sold to you for the remaining amount at the BUY price quoted. The value in the gold locker is calculated on the live SELL price, i.e. the price at which the gold is bought back from you and sold in the commercial bullion market. This is different from the BUY price and therefore the locker value would be different from the amount initially paid.