Tax audit on petrol pump

Good evening sir,
I was given a tax audit case for a petrol pump.
Every year the evaporation loss (difference between closing stock as per books and dip stock data) is deducted from closing stock as per books and accounted accordingly. But I've got evaporation gain for diesel this time and I cross checked dip data and sales again and also rechecked with the client. Since 2 years they are facing IT Scrutiny. I want your suggestion as to how I can account that evaporation gain. Please kindly help me.