GST on sale of used car

WDV of car is Rs. 12L. It is sold for Rs. 14L. GST will be charged on profit margin at the rate of 18% i.e. CGST Rs.18000 and SGST Rs.18000. The taxpayer is not a used car dealer, but is registered under GST. The buyer too is registered under GST. So the value of the B2B invoice will be Rs.200000+CGST 18000 + SGST 18000 only, and not of the entire consideration of Rs.14L received?

Thank you