How did a simple error cause ₹12.9-crore loss to West Bengal in a deal with Flipkart?

A CAG report highlighted that West Bengal Industrial Development Corporation (WBIDCL) incurred a ₹12.86-crore loss due to a simple calculation error in the allotment of land to Flipkart subsidiary Instakart in Nadia. WBIDCL fixed the land's price without excluding water bodies from total project area. WBIDCL's own policy excludes water bodies from calculations as they have no industrial uses.